Thanks to @siracusa for this one; I noticed it being retweeted this morning, and figured more than a few folks might be interested in it.
If you're one of the people who preferred the "maximize on click" behavior of the green button in iTunes 9 (which vanished in iTunes 9.0.1, as the update reverted to the pre-iTunes 9 "show mini player" behavior), quit iTunes 9, and run this command in Terminal:
defaults write com.apple.iTunes zoom-to-window -bool YES
Relaunch iTunes 9, and the green button should now maximize the window; Option-clicking should get you the mini player (I haven't actually tested it myself, but the tweets say it works).
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090924075333329