If you run Linux, you can configure the XScreensaver to display RSS feeds by editing the .xscreensaver file (config file) as follows:

textMode: url
textLiteral: XScreenSaver
textFile:
textProgram: fortune
textURL: http://newsrss.bbc.co.uk/rss/newsonline_uk_edition/front_page/rss.xml

The above example snippet sets the screensaver to display an RSS feed from the BBC News website!

I particularly like the OpenGL Fliptext screensaver…