Oh yes, I couldn't live without OpenOffice.org for my writing. And RocketDock, how could I forget that! It's like Mac's Dock, only for Windows. Then there's 7-Zip, of course, and a cool little app called Frameworkx that removes the shortcut overlay image on desktop icons in Vista.

Let's see... The GIMP is a pretty obvious one, but what about Switcher? It's similar to Exposé for Mac.