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.)

The easiest solution is the widget Wallify. It is free, with a "Pro" version available, but the free version basically does the same thing that CajunLuke suggested, but without having to use the Terminal.

You can select most of your screen savers directly from the menu on the widget, but specific photo slide-show style screensavers don't appear as an option. To use these kinds of screensavers, you can choose them using the System Preferences > Desktop & Screen Saver, then on Wallify just select "Default", and it will use whatever you chose in System Preferences.

You may want to try RandomExtra.screensaver This screensaver allows you to select a specific screensaver for multiple monitors. Following the very simple install notes, you can have this screensaver installed in seconds. Once installed open your System Preferences and go into your "Desktop & Screen Saver" pane. Find the newly installed "RandomExtra" Screen Saver and click on options. Once inside the Screen Saver options choose the "Extra" tab and you will find some options for what you may be wanting to do.