Is it possible to show a screensaver on a secondary monitor while using the primary monitor? I have an iMac with a large format display set up as a secondary monitor that we use as a television for watching movies.  When I am just using the iMac, I would like for the secondary display to display something interesting rather than just the wallpaper.

Is it possible to set up a screensaver that appears on the second monitor (I really like the iPhoto slideshow) while allowing me to use the primary iMac monitor?

I would even be happy if it wasn't technically a screen saver, but just any sort of slideshow that could be displayed on one monitor while I work on the other.  Currently if I play a slideshow in iPhoto, the other monitor goes blank. :(
You can set your screensaver to be your desktop background (link to source).

To do so, run this in the Terminal:

/System/Library/Frameworks/ScreenSaver.framework/Resources/ScreenSaverEngine.app/Contents/MacOS/ScreenSaverEngine -background


This works on both monitors (tested just now in Lion), so as long as you don't put any windows on the other monitor, it'll just show the screensaver. (Unfortunately, the screensaver will also be behind all of your windows on the screen you're using. I hope you really like your screensaver.)