I keep a plethora of web sites saved for use. My laptop has died twice now and I've lost most of them and it leaves me feeling almost crippled!
The ones I use most often are:
http://www.usps.com - website for the postal service (I use it mostly for zip codes)
http://www.searchbug.com - a cross search engine for phone numbers and business info
http://www.urbandictionary.com - dictionary for modern terminology and slang (Blushing) I use this alot.
http://www.rulesofthumb.org - mostly fun, just lots of rules of thumb.
http://www.newsmeat.com - Find out who donated how much to whose campaign.
For fun...
http://www.overheardinnewyork.com - Sometimes funny, sometimes depressing
http://www.engrish.com - No wonder we have such a hard time communicating
http://www.NMDB.com - people profiles of all kinds
http://www.thetruth.com - because I hate the cigarette industry just that much
http://www.lolcats.com - everyone knows this site by now. I don't know why but the language just cracks me up.
Oh well, and of course, HotBytes.