My Favorite Internet Week 1
This website lets you ride around on a line in 3D. It's pretty entertaining for a few moments because you can continually make more shapes. I like little interactive timewaster websites like this.
Weavesilk lets you create interesting images with an interesting interactive generator that makes light neon strokes. You can make some great backgrounds like this. The UI is very easy to navigate and it feels like you learn everything naturally.