If you download and install Xcode, a very handy app called Quartz Composer is included which has a built-in mode for creating screensavers. Perhaps somebody who has Xcode installed on their machine can give you just the app itself. I don't believe it has any Xcode dependencies at all. You can even open up Apple's own screensavers with Quartz Composer to find out what they do. It is quite a cool app!
I modified Apple's RSS Visualizer to present my school's RSS feed a little better than what the Apple & change the default colors to match my school's colors.
Unfortunately, the feed itself is not kept as up-to-date as it should, and is missing important things such as sporting events. I had fun though, and spent many hours tinkering before I dropped the project.