Two days ago, I downloaded the Stumbleupon toolbar for Firefox.
As an aside, if you're still using Internet Explorer instead of Firefox, you need to switch immediately. Here's a link for your convenience. Stumleupon does work with IE, but let's be serious, it's an inferior browser. ;)
Anyway, Stumbleupon is fantastic fun! The Stumbleupon fairies index websites using 500+ sub-categories organized into 14 major categories, including everything from film noir to car parts to beer to reggae. You choose the categories that interest you (as many or as few as you like) and then you begin "stumbling."
As you stumble, you get to rate the sites you come across. If you like a site, it is stored in your Stumbleupon profile. Just to give you a taste, here are some of my favorites:
1) Album Art - type in the name of a band, singer, or album and this site finds cover art for you.
2) Scott Wade's Dirty Car Art Gallery - this guy creates art on dirty windshields!
3) Pipecleaner Dance - use your keyboard to make the pipecleaner man dance.
4) Mr. Picassohead - use the shapes to make a funny face.
5) And, my personal favorite, Jackson Pollock - a blank screen and a mouse are all you need to make a Pollock-esque creation. Click for a new color.
Try it. You'll like it. Depending on the categories you choose, you might even find something useful, rather than just some fun time wasters...