If you'd like even more screen savers, the Developer Tools includes two additional ones you can use: Retro and Security. Retro takes your screen, gives it a sepia tone, and bounces it up and down. Your friends will run up to you screaming, "You're monitor is broken!" Security simply takes a bunch of pictures from your iSight and displays them in a grid. It really is awesome.
You'll find the screen savers here:
/Developer/Examples/Quartz Composer/Compositions/Screen Savers
To install, copy them into your user's /Library/Screen Savers folder. Voila! They'll show up in the Other section of the Screen Savers tab of the Desktop & Screen Savers System Preferences panel.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20071103185237239