If you're moping around because you can no longer watch some of your favorite old Mac OS X screen savers because they were never updated for 10.6 (and never will be because the developers have dropped off the face of the Earth taking their source code with them), take heart.
The free application SaverPreview (from this page; scroll down to find it) can still play those old savers in a window, which you can then zoom to fit the screen if you want. If you have Rosetta installed, SaverPreview should even be able to play PowerPC-only screen savers, though I haven't tried this.
Now you can while away the time doing something completely pointless, like playing old DOS games in an emulator.
[robg adds: This hint described how you might also be able to recompile older screen savers yourself, if the source was available.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20100211150636336