Passively keep up to date on any topic

Set your screensaver to display the results of a twitter search.

Here's how you do it on a Mac:

1) Go to http://search.twitter.com and search for your topic of interest
2) Copy the "RSS Feed" link
3) Paste the link into Apple's RSS Visualizer Screensaver

Now whenever your screensaver activates, you'll be greeted with the latest, relevant tweets. We've already found this to be useful!