If you like working with full-screen windows, you might want to try Right Zoom, a nice little freeware which modifies the behavior of the green button on OS X windows. Once installed, clicking the green button will always expand a window to full screen size.
Right Zoom runs in the background without a dock icon, and as far I can tell, uses few resources. This older hint introduced shortcuts for doing this using the keyboard, but I didn't see anything for changing the behavior of the actual green button.
[robg adds: I haven't tested this app, but given that "how can I make the green button fully expand windows?" is one of the most-common email inquiries I receive, I thought it was worth sharing.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090302023042371