A couple other great ways to waste your workday hours...
First of all, besides being the place to find everything, from roommates to used air conditioners, craigslist.org also has a "Best Of" Craigslist section, where they put all the ridiculous posts people have deemed hilarious or otherwise notable, such as this post about squirrels, and this classic public defender one.
I also have to give love to Homestar Runner.com, the funniest use of flash cartoons online right now. I recommend the Children's Book email, as well as the emails called "Dragon" and "Japanese Cartoon".
Wikipedia.org is about the most valuable educational tool on the web - you can learn a little something about anything, ever. Like a massive, multi-language, free encyclopedia. I recently used to to learn how microwaves work.
And, of course, shoutouts to two of my blogger friends, the finger-on-the-pulse comedian/weird-news generator Sam Greenspan, and the politically savvy ghetto-slanger Pat Stack. I particularly like his whale article.