ImageJ great scientific software that supports macro writing…PC version of NIH Image..
NIH Image Original Freeware Image Analysis for the Mac (lots of user support…)
Irfanview (great freeware for image management–has batch resizing, renaming etc).
Exview (even better than Iranview for some things)
GIMPM (Photoretouching tool-not for scientific use..)
Windirstat (really good for finding how space is used on your hard drive…)
Belarc Advisor (hardware and software analysis tool)
(for between-experiments free time…)
Audiograbber (great for copying vinyl and CDs (that you own, of course)
TrueCrypt (“Free open-source disk encryption software for Windows Vista/XP, Mac OS X, and Linux” (from publisher) -recommended by ZDnet)