http://www.openoffice.org/ - Linux based open sourced word processing suite. I've used this on OS X and Windows. It works great, has all the other programs Office has (spreadsheets, presentation slides), can open Office files and is continually updated. Downside is... it's in Java... chugga chugga chugga
http://www.barebones.com/products/textwrangler/index.shtml - More of a text editor in the traditional sense. I use this to edit all the code for SP. It does really well with language markup. Could definitely be used for word processing.
Doesn't La Salle provide free Office suite for their students?