CamStudio for video casting
Puran Defrag free for defragmentation of harddisk
WinDirStat for visualising the space used by various apps ... awesome app ..
Wireshark for Packet Capturing and learning about packets especially for networking students.
GNS3 for router.switch.hub etc Emulation (not simulation like packet tracer) .. with this app u can emulate real routers etc..
inSSidr for wifi routers signal strength determination etc..
Gom Player awesome media player very fast and beautiful interface
Lingoes .. excellant app for translation and offline dictionaries.. u can search a single word in all dictionaries .. it has hundreds of dictionaries...
nrgtoiso to convert nero nrg to iso so easily be mounted..
Google Picassa awesome image viewing app.. it zooms where u point ur pointer at .. and very fluid performance on my p3 computer.
Opera Browser simply the best.. i have been using it since it was paid app... that means more then a decade.. excellant smooth scrooling a lot of features
Sysinternals suite including Process Explorer
Circuit Simulator applet by falstad .. simply awesome
and a ton of more..