The Drops Saver is freeware. It's free to use any way you please. Donations are much appreciated!
This OS X screen saver draws patterns of raindrops on your desktop.
There's a configuration panel to set the number of drops, drop size, drop color and a blanking screen option. In version 1.1.1 I retooled the screen saver to use a transparent window so any activity behind the screen saver (when the screen isn't blanked) will be shown. Performance has improved quite a bit as well.
For version 1.1.2 I removed the screen Capture on the screen saver preview so it won't crash System Preferences in Tiger!
This has tested to work on Jaguar (10.2) and above.
The source is included in the disk image so go crazy. If you do modify the code I'd appreciate it if you send me your improvements.