Stumble
I've just added StumbleUpon to my browser - if you're using Firefox, like I do, and if you like to waste ungodly amounts of time discovering random stuff on the internet, like I do, StumbleUpon is a must.
And if you're not using Firefox (at least on a computer where you're not forced by some crappy IT department to use Internet Exploder), what the hell's wrong with you? Go download that sumbitch, right now! I'll keep myself entertained.
Mahna mahna...doot do do do do...Mahna Mahna...doot do do do...
Back? Okay, great! Now go get the StumbleUpon add-on. It's seriously one of the coolest things ever. I've been playing with it for an hour now, and discovered dozens of cool things that I otherwise would never have seen. Like this. And this. And this. And this. I told the thing that I was interested in drawing, in photography, in magic tricks and in astronomy (among other things), clicked a button, and it took me to all these cool sites.