Freebies:
Calendar Magic Great freeware calendar toolkit plus calculator and loads of other things.
Countdown program Good version of the TV game...for end of term and other such occasions.
A Dictionary of Units Forgotten how many pecks make a bushel? or want to know some history of measurements?
Graph Paper Printer Print your own graph paper. Incredibly useful and very versatile, even prints manuscript paper for music. The link is for the more developed paid for version. The last freeware version, which is still good, can be found here.
K9 A free bayesian anti spam filter. I get masses of spam and could not live without this. It learns from it's mistakes. You need to do some setting up and check on it a bit at first but it doesn't take long for it to be effective.
Power Toy Graphical Calculator A free extra from microsoft. Also check out the other power toys.
Pricelessware Huge list of good freeware programs.