One of the best non-Apple based applications I've download through the years is a program called
Dock Spaces. (
http://www.nscoding.co.uk/ ).
For those using OS X 10.5 or 10.4, it allows users to have multiple docks, which can be different ones in Spaces windows. Easy to use, and brilliant in execution. Best of all it is free, with a 'donation' - which I happily did!
One dock with all my astronomical applications, and another with all my current working documents.
Made "Staff Pick" on the Apple home site.
(Disclaimer: I have no association personal with this application.)