Well i have to say this is a very enjoyable OS. It comes with a lot of nice programs that I’m really enjoying. here’s a couple of things i insist on checking out.
- Colloquy (IRC Client)
- Skype Mac Video (beta, but works with iSight)
- Adium (multi protocol IM client)
- CyberDuck
- iAlertU
Out of those i would definately insist on trying iAlertU. After installing it and launching it press menu and hold to turn the alarm on on your mac! Get your mates by putting your mac on their seat etc 
The latest version also triggers all buttons, touchpad, removal of psu and if you open the Lid.
Colloquy is another must if you use IRC. This is the best looking GUI irc client I’ve ever seen! It also has some cool features. Like you can set it to show everything in novel mode i.e.:
[2:50PM] “hey L hows it going?,” asked russo.
[2:51PM] You were promoted to operator by L.
[2:52PM] “Why isn’t anyone ever in #balzac? It’s frustrating i must say! My word L you’ve just promoted me.,” said russo.
etc 
get a macbook losers!