because I think a person's chathack is as personal as their homepage.
I warn you though, chathacks are much harder to make. If you don't have some experience with computer programming, I would not advise the attempt.
Also, please be considerate when you design (and use) it. Follow the rules of nettiquette or expect the worst. You are responsible for whatever buttons you make. Most homepage providers will not stand for offensive content.
some other stuff:
ScriptTutor an introduction to the JavaScript language
Auto DropList activated when the item in the list is clicked
Parameters two buttons can share the same function with different results.
math calculating is easy too
Booleans the famous If/Then statements that separate the computers from the calculators.
Cookies I know you want 'em. Memory ooooooo.

My really nice homepage