I found out about this software on a podcast earlier today ... it allows you to create multiple virtual desktops ... so you can switch between screens dedicated to different apps ... such as work, mail, surfing, etc ... pretty cool ... especially for laptop users.
http://developer.berlios.de/project/...?group_id=3463
http://www.versiontracker.com/dyn/moreinfo/macosx/21594
I downloaded it earlier this evening ... seems very useful.