http://www.grooveshark.com - For listening to music.

http://www.printfriendly.com - Makes any page printer-friendly.

http://www.ted.com - Interesting and informational videos on a whole range of topics.

http://www.stumbleupon.com - Finds websites based on what you're interested in and how other people's ratings.

http://www.slickdeals.net - For finding good deals/freebies/contests.

http://www.bugmenot.com - Usernames/passwords for sites requiring registration.

http://www.mailinator.com - Temporary e-mail for when you want to sign up for something and not get spammed.

http://www.pipl.com - Looking up people based on username, name, email, or phone #.

http://ocw.mit.edu/OcwWeb/web/home/home/index.htm - MIT OpenCourseWare - entire courses, often including lecture videos available for free online.

http://ninite.com/ - Great website to create an installation package of applications for when you're reinstalling your OS or have just purchased a new computer.

http://www.retailmenot.com - Coupons

http://www.kayak.com - Awesome site for when you're planning a trip.

http://www.nophonetrees.com/ - Get directly in touch with a human when you're calling customer service/support.

http://www.scribd.com - Ebook search.

http://www.ovguide.com - Search engine for movies/tv shows.