Old Standby
When I'm at work, my Mac sits beside me as my window to the outside world. Sometimes its my "with friends" Twitter stream, sometimes it's a live webcam or two, and sometimes it's Digg Labs' "swarm."
A lot of the time, though, it's this "newsmap" page.
Taking your typical linear scrolling news ticker to the next level, it shows a spectrum of news stories (configurable by topic and region). The "hotter" the story, the larger the item is on screen. It's a few years old now (turns out I blogged about it in March 2004!), but still quite cool.
I guess I'm basically using these as glorified screen savers, but I'll take up-to-date tidbits over flying toasters any day.