One of the pieces of software that I use the most is software that does screen captures. Of course, you can always capture an entire Windows screen by simply choosing PRINT SCREEN and pasting into a document or image-editing program. (And, on a Mac, there are easy ways to do this within the operating system!) However, for training purposes, sometimes you just want to include part of a page or just an open window. There are commercial programs that do this well and include enhanced features (i.e. ScreenPrint Platinum and Screen Hunter 4.0 Pro and Plus), but there are some free programs that also get the job done in a pinch.
ScreenHunter 4.0 Free
List of other screen capture utilities
...two lists of freeware, shareware, and commercial screen-capture programs