- Cygwin (with ssh, scp, git, svn, grep, sed... X is nice too and so is MinTTY)

- Emacs (the Windows executable is a bit of a pain to integrate with the Cygwin side)

- GIMP

- Firefox (with Firebug)

- Chrome (nice developer support too)

- Pidgin (because I have friends on MSN, Gtalk, ICQ, iChat and IRC)

- Skype (because not everyone can type)

- Sysinternals (running pagedefrag is like brushing the machine's teeth)

- JDK (because it's nice to be able to compile Java code from time to time). You may want it with Eclipse or NetBeans or both, but writing Java code is not that nice.

- Freemind (another reason to have a JRE)

- Openoffice (because you really don't want to save .doc files)

I think that covers everything I need on a Windows box. Too bad Gnome support is so minimal on that OS.