There are a few apps for OSX that handle virtual desktops like X11 windowmanager often implement. I've found one now (thanks to The Unofficial Apple Weblog) that has a few advantages over the others I've tried:

• Open Source

• Not as intruding (can be configured to stay in the menubar)

• Actually uses the power of Quartz.

Check out a few of the screen transition movies (QuickTime) on the website

I have it set to two desktops, menubar pager only, no bezel thingo and a fast cube effect. I like it, a lot.