Since I’m doing desktop analysis: I use four spaces.

1. General. Browsing, mail, IRC, etc. All here.
2. Virtual Machine consoles go here (I run an Ubuntu VM for Apache, rather than natively through OSX, since this way it’s resilient to OSX software upgrades), also Fireworks, Photoshop and OmniGraffle when they’re open. Sometimes empty (and so currently segregating to-do lists)
3. Code. Terminals and Textmate.
4. Preview. Firefox, Safari, and IE8 (in IE7 mode) through VMWare.