Find files of a specific type (eg: .pdf, .mp3, .zip)
web development guidelines filetype:pdf
http://www.google.com.au/search?q=web+development+guidelines+filetype%3Apdf
Find directory listings
intitle:"index of" templates
http://www.google.com.au/search?q=intitle%3A%22index+of%22+templates
Find pages with keywords in the url
allinurl:seo tips
http://www.google.com.au/search?q=allinurl:seo tips
Search for similiar terms
~cheap web design -cheap
http://www.google.com.au/search?q=~cheap web design -cheap
Search within a specific site
google site:eisabainyo.net
http://www.google.com.au/search?q=google+site%3Aeisabainyo.net
Websites that are linked to a website
link:https://eisabainyo.net
http://www.google.com.au/search?q=link%3Ahttp%3A%2F%2Feisabainyo.net
Google as a world clock
time in Sydney
http://www.google.com.au/search?q=time+in+Sydney
Google as a dictionary
define:query
http://www.google.com.au/search?q=define:query
Google as a conversion calculator
160cm in feet
http://www.google.com.au/search?q=160cm in feet
Google as a weather report
weather:sydney australia
http://www.google.com.au/search?q=weather:sydney australia
[tags]google, search engine, tips, search operators, google hacks[/tags]
Thanks for the good tips!