All of them.
http://www.google.com/search?
Google's URL. If you didn't know that bit, you're probably Amish.
q=query+goes+here
The query string. Words are separated by + signs.
Everything from here on in is preceded by an & sign, as it's tagged on to the end. Here's where (if you have no girlfriend), things get interesting...
as_epq=query+goes+here
Results must include the query, in the word order displayed.
Shows as "query goes here"
as_oq="query+string"+goes+here
Results must include one or more of the words in this string. Basically, it's like a more advanced version of the one above, using an "or" filter. Thus, every result must have the main initial query, and one or more of the sets of terms in these strings.
Shows as "query string" OR goes OR here
as_eq=don't+include+these+words
Results must NOT include any words in this string.
Shows as -don't -include -these -words
num=xx
Controls the number of results shown. Must be a numeric value, and can be anything up to 100. Doesn't work with fractions. I've tried.
as_filetype=extension
Only returns results that end in .extension. Currently supports any input. Try it - make a file with a random extension, get it indexed and do a search. Also shows that as long as it validates to something, Google can and will index it. Something to think about...
Shows as filetype:extension
as_sitesearch=example.com
Limits results to just the site you choose.
Shows as site:example.com
as_qdr=x
Swap out x for the following to limit the search to only files first indexed in:
  • d - the previous 24 hours
  • w - the previous seven days
  • m - the previous month
  • y -  past year
  • mn - the previous n number of months. So m2 would be the previous two, m3 would be three, and so on. Does work into double digits
as_rights=xxx
Limits the search to files/pages that have certain rights. The options are:
  • (cc_publicdomain|cc_attribute|cc_sharealike|cc_noncommercial|cc_nonderived) - free to use or share
  • (cc_publicdomain|cc_attribute|cc_sharealike|cc_nonderived).-(cc_noncommercial) - free to use or share, including commercially
  • (cc_publicdomain|cc_attribute|cc_sharealike|cc_noncommercial).-(cc_nonderived) - free to use, share, or modify
  • (cc_publicdomain|cc_attribute|cc_sharealike).-(cc_noncommercial|cc_nonderived) - free to use, share, or modify commercially
If you want to make up your own, put the bits you want in brackets, separated by pipe characters (|), and exclude the bits you don't by putting them in brackets, preceded by .- and again pipe-separated.
allintitle%3Asearch+terms
This is actually appended to the q= parameter, hence a search for fishing with the allintitle term "sea bass" would require the following query:
q=fishing+allintitle%3Asea+bass
Shows as allintitle:search terms
N.B. This also works with allintext to search page body text, allinurl for searching the URL, and allinanchor for finding sites that are linked to with certain anchor text.
nnn..yyyy
Like the allin parameters, this is actually appended to the q= parameter. What this does though is let you search for results between numeric ranges. For example, if you wanted to find documents with numbers between 15 and 100, you'd put in 15..100. Very useful for finding products in a price range, when combined with the site limiter. Works with $, £, and other such things.
Shows as query 15..100
%2Bterm
Again, this is appended to the q= parameter. The %2B is actually the + sign encoded, and will return results featuring only the term used, with no pluralisations, alternate tenses, or synonyms.
Shows as +term
~term
Another one that's appended to the q= parameter. Returns results for the term used and synonyms.
Shows as ~term
define%3Aword
Yet another q= parameter add-on. Returns definitions for the word you put in.
Shows as define:word
term * term two
And another q= parameter add-on. Returns results with listings that contain both words, with other words between them.
n+n2, n-n2, n/n2, n*n2, n^n2 and n% of n2
Google's calculator functions. They are, in order, add, subtract, divide, multiply, raise to the power of, and return x percentage of.
safe=active
Sets safe search to on. To turn it off, change active to images.
as_rq=example.com
Finds sites Google thinks are related to the URL you put in.
Shows as query related:example.com
as_lq=example.com
Finds sites that link to the URL you put in.
Shows as query link:example.com
newwindow=n
Opens clicked listings in a new window. Very useful for opening lots of documents at a time, for competitor research. Set to 1 to activate, and 0 to turn it off.
pws
Controls whether personalised search is on or not. Set to 1 to activate, and 0 to turn it off.
adtest=on
Turns off AdWords database connection, so your browsing won't show up as an impression, and will disable the URLs. Set to on to activate, and off to turn it off.
btnG=Search
Simulates a click on the normal Google results buttpm. Change to btnI to get the I'm Feeling Lucky button result.
ie=
Controls the input encoding settings. This defaults to UTF-8, and is worked out server-side, hence changing it doesn't do anything.
oe=
Controls the output encoding settings. Works in the same way as ie, so you can tinker away, but it won't do anything.
&hl=value
Changes the interface language. I won't list them all here, but you can find them all here.
lr=value
Limits the languages used to return results. Not hugely effective. That said, here's the list of all of them:
  • lang_ar - Arabic
  • lang_hy - Armenian
  • lang_be - Belarusian
  • lang_bg - Bulgarian
  • lang_ca - Catalan
  • lang_hr - Croatian
  • lang_cs - Czech
  • lang_da - Danish
  • lang_nl - Dutch
  • lang_en - English
  • lang_eo - Esperanto
  • lang_et - Estonian
  • lang_tl - Filipino
  • lang_fi - Finnish
  • lang_fr - French
  • lang_de - German
  • lang_el - Greek
  • lang_iw - Hebrew
  • lang_hu - Hungarian
  • lang_is - Icelandic
  • lang_id - Indonesian
  • lang_it - Italian
  • lang_ja - Japanese
  • lang_ko - Korean
  • lang_lv - Latvian
  • lang_lt - Lithuanian
  • lang_no - Norwegian
  • lang_fa - Persian
  • lang_pl - Polish
  • lang_pt - Portuguese
  • lang_ro - Romanian
  • lang_ru - Russian
  • lang_sr - Serbian
  • lang_sk - Slovak
  • lang_sl - Slovenian
  • lang_es - Spanish
  • lang_sv - Swedish
  • lang_th - Thai
  • lang_tr - Turkish
  • lang_uk - Ukrainian
  • lang_vi - Vietnamese
  • lang_zh-CN - Chinese Simplified
  • lang_zh-TW - Chinese Traditional
cr=countryXX
Limits the search results to pages/sites from certain locations. Change XX to any of the following, to limit the results:
  • AF - Afghanistan 
  • AL - Albania
  • DZ - Algeria 
  • AS - American Samoa
  • AD - Andorra
  • AO - Angola 
  • AI - Anguilla
  • AQ - Antarctica
  • AG - Antigua and Barbuda
  • AR - Argentina
  • AM - Armenia
  • AW - Aruba
  • AU - Australia
  • AT - Austria
  • AZ - Azerbaijan
  • BS - Bahamas
  • BH - Bahrain
  • BD - Bangladesh
  • BB - Barbados
  • BY - Belarus
  • BE - Belgium
  • BZ - Belize
  • BJ - Benin
  • BM - Bermuda
  • BT - Bhutan
  • BO - Bolivia
  • BA - Bosnia and Herzegovina
  • BW - Botswana
  • BV - Bouvet Island
  • BR - Brazil
  • IO - British Indian Ocean Territory
  • BN - Brunei Darussalam
  • BG - Bulgaria
  • BF - Burkina Faso
  • BI - Burundi
  • KH - Cambodia
  • CM - Cameroon
  • CA - Canada
  • CV - Cape Verde
  • KY - Cayman Islands 
  • CF - Central African Republic
  • TD - Chad
  • CL - Chile
  • CN - China
  • CX - Christmas Island
  • CC - Cocos (Keeling) Islands
  • CO - Colombia
  • KM - Comoros
  • CG - Congo
  • CD - Congo, Democratic Republic
  • CK - Cook Islands
  • CR - Costa Rica
  • CI - Cote d'Ivoire
  • HR - Croatia
  • CY - Cyprus
  • CZ - Czech Republic
  • DK - Denmark
  • DJ - Djibouti
  • DM - Dominica
  • DO - Dominican Republic
  • TL - East Timor
  • EC - Ecuador
  • EG - Egypt
  • SV - El Salvador
  • GQ - Equatorial Guinea
  • ER - Eritrea
  • EE - Estonia
  • ET - Ethiopia
  • FK - Falkland Islands (Malvinas)
  • FO - Faroe Islands 
  • FJ - Fiji
  • FI - Finland
  • FR - France
  • GF - French Guiana
  • PF - French Polynesia
  • TF - French Southern Territories
  • GA - Gabon
  • GM - Gambia
  • GE - Georgia
  • DE - Germany
  • GH - Ghana
  • GI - Gibraltar 
  • GR - Greece
  • GL - Greenland 
  • GD - Grenada
  • GP - Guadeloupe 
  • GU - Guam 
  • GT - Guatemala 
  • GN - Guinea
  • GW - Guinea-Bissau 
  • GY - Guyana
  • HT - Haiti 
  • HM - Heard and McDonald Islands
  • HN - Honduras 
  • HK - Hong Kong
  • HU - Hungary 
  • IS - Iceland
  • IN - India 
  • ID - Indonesia
  • IQ - Iraq 
  • IE - Ireland
  • IL - Israel 
  • IT - Italy
  • JM - Jamaica 
  • JP - Japan
  • JO - Jordan 
  • KZ - Kazakhstan
  • KE - Kenya 
  • KI - Kiribati
  • KW - Kuwait 
  • KG - Kyrgyzstan
  • LA - Lao People's Democratic Republic 
  • LV - Latvia
  • LB - Lebanon 
  • LS - Lesotho
  • LR - Liberia 
  • LY - Libya
  • LI - Liechtenstein 
  • LT - Lithuania
  • LU - Luxembourg
  • MO - Macau
  • MK - Macedonia 
  • MG - Madagascar
  • MW - Malawi 
  • MY - Malaysia
  • MV - Maldives 
  • ML - Mali
  • MT - Malta 
  • MH - Marshall Islands 
  • MQ - Martinique
  • MR - Mauritania 
  • MU - Mauritius
  • YT - Mayotte 
  • MX - Mexico
  • FM - Micronesia 
  • MD - Moldova
  • MC - Monaco 
  • MN - Mongolia
  • MS - Montserrat 
  • MA - Morocco
  • MZ - Mozambique 
  • NA - Namibia
  • NR - Nauru 
  • NP - Nepal
  • NL - Netherlands 
  • AN - Netherlands Antilles
  • NC - New Caledonia 
  • NZ - New Zealand
  • NI - Nicaragua 
  • NE - Niger
  • NG - Nigeria 
  • NU - Niue
  • NF - Norfolk Island 
  • MP - Northern Maria
  • a Islands 
  • NO - Norway
  • OM - Oman
  • PK - Pakistan 
  • PW - Palau 
  • PS - Palestinian Territory
  • PA - Panama 
  • PG - Papua New Guinea
  • PY - Paraguay 
  • PE - Peru
  • PH - Philippines 
  • PN - Pitcairn
  • PL - Poland 
  • PT - Portugal
  • PR - Puerto Rico 
  • QA - Qatar
  • RE - Reunion 
  • RO - Romania
  • RU - Russian Federation 
  • RW - Rwanda
  • KN - Saint Kitts and Nevis 
  • LC - Saint Lucia
  • VC - Saint Vincent and the Grenadines 
  • WS - Samoa
  • SM - San Marino 
  • ST - Sao Tome and Principe
  • SA - Saudi Arabia 
  • SN - Senegal
  • CS - Serbia and Montenegro 
  • SC - Seychelles
  • SL - Sierra Leone 
  • SG - Singapore
  • SK - Slovakia 
  • SI - Slovenia
  • SB - Solomon Islands 
  • SO - Somalia
  • ZA - South Africa 
  • GS - South Georgia and The South Sandwich Islands
  • KR - South Korea 
  • ES - Spain
  • LK - Sri Lanka 
  • SH - St. Helena
  • PM - St. Pierre and Miquelon 
  • SR - Suriname
  • SJ - Svalbard and Jan Mayen Islands 
  • SZ - Swaziland
  • SE - Sweden 
  • CH - Switzerland
  • TW - Taiwan 
  • TJ - Tajikistan
  • TZ - Tanzania 
  • TH - Thailand
  • TG - Togo 
  • TK - Tokelau
  • TO - Tonga 
  • TT - Trinidad and Tobago
  • TN - Tunisia 
  • TR - Turkey
  • TM - Turkmenistan 
  • TC - Turks and Caicos Islands
  • TV - Tuvalu 
  • UG - Uganda
  • UA - Ukraine 
  • AE - United Arab Emirates
  • GB - United Kingdom 
  • US - United States
  • UM - United States Minor Outlying Islands 
  • UY - Uruguay
  • UZ - Uzbekistan 
  • VU - Vanuatu
  • VA - Vatican 
  • VE - Venezuela
  • VN - Viet Nam 
  • VG - Virgin Islands (British)
  • VI - Virgin Islands (U.S.)
  • WF - Wallis and Futuna Islands 
  • EH - Western Sahara
  • YE - Yemen 
  • ZM - Zambia
  • ZW - Zimbabwe