What software do you run on your second monitor?

My desktop setup consists of a primary 30" LCD with a second 20" LCD off to the side.

I use both monitors a lot, especially when I'm coding up a new site and can use the side monitor to show the website with the primary monitor being used for the code editing.

However, sometime the second monitor sits idle and I'd like to have it run a little app in the background (like a virtual fish tank).

I've done a lot of searching but to my surprise there's not a lot of virtual "pet" type applications available (maybe a good startup project).

Do any hackers have any good apps that I can run (maybe a flash projector of sorts) that I can run on my second monitor to add a bit of entertainment when it's not in use?

Here's an example of a nice little goldfish application, but I'm looking for something that will run full screen.

http://abowman.com/google-modules/fish/

What do you do with your second monitor when it's sitting there idle?