I have been training people for the last 10 years and enjoy taking people to the next level of learning. There are 50 Tips for you to try, in the full Version there are over 400 Tips. (You'll need Adobe Acrobat Reader to view this Document.)
Symtometer
Type Inspector
CrimeBooks.Net
Chalksoft
GameGlade.com
FunGamesGalaxy.com
F-Group Software
GINGER
Altavi.com
KFOO Software
Urban Pursuit, Inc.
Jonathan Freeman
Jason M. Greene
Compress PST Files