Your Dev Environment
mmphosis: MacBook 2Ghz Intel Core Duo, 2GB 667 Mhz DDR2 SDRAM
http://www.virtualbox.org/
I've found a use for Spaces.  I put each fullscreen virtual machine in it's own space.
Space 1 - Mac OS X (native)
Space 2 - Windows (virtual machine)
Space 3 - Ubuntu (virtual machine)
I keep networking turned off in Windows.  Files are shared locally by VirtualBox between Windows and Mac OS X.