I can't believe I just learned this today. However, if you're like me, you may not have realized how to add a buddy to your iChat buddy window without using the Address Book. People who knew me saw that I was online, and so would start a chat. But I couldn't figure out how to put them in my Buddy List just from the chat window.
Well, by clicking on the leftmost button (with the person image) in the main iChat window, you open a drawer. You can then drag the user's icon from the drawer to your buddy list. Voila! I kept tryng to drag directly from the chat window itself. I hope this helps someone else, too!
[robg adds: Yes, this is a basic hint. And originally, I wasn't going to run it, believing that it was a clearly documented obvious feature. However, a quick run through the iChat help files shows no mention of using the drawer to add buddies to the buddy list (maybe I'm just going blind?). All the help file mentions is using the "+" button in the buddy list window to add via the Address Book. Strangely, I'd never done anything other than dragging from the drawer area; until recently, I'd never even tried the "+" button in the buddy list window!]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030410224101120