http://www.apple.com/downloads/
Click on All Downloads on the left. Lots of good freeware and shareware in there.
Also take a look at the iLife apps that come with it. They're fairly decent. Darlet #1 did an excellent class project with the movie and dvd apps.
Open Office is available for the mac and does a nice job.
Borrow or buy
Mac OS X Leopard: The Missing Manual. Very useful for learning all the little tricks.