Interesting thread, and some interesting software on that list. I guess our choices say a lot about us....

For me, using windows XP Media Edition:
maptool (obviously)
stickies - great way to keep notes and you can pin them to folders or apps. I get an initiative sticky whenever I open up maptoolfor example.
Open office - great for quickly pdfing documents
dropbox - a good free 2GB of filesharing and online backups that synchs with your computer
Picasa - much nicer previewer than windows, though really doesn't handle cmyk files.
emacs - well, not for everyone I'm sure, but it does help with coding
posterazor for cutting up large images into pdfs
Core ftp lite - good little ftp program
pdftk builder - great for collating pdfs into one document, or breaking up pdfs into separate documents

Other useful bits and pieces - xming and putty for working remotely, imagemagick for command line image processing.