For Mac Kids:
CrossOver
If you have an Intel mac, this is a great, seamless Wine loader, and works with most Windows software.
Quicksilver
A very nice launcher app, built around applescript, with a ton of built in functionality.
Genius
A nice program for when you need to memorize a lot of information. Works kinda like flash cards.
Little Snitch
Catches any outbound network traffic, and allows you to control access, for various applications. Great security tool.