37 Signals

I’ve heard of 37 Signals suite of software but never tried it out. I still haven’t tried it out, but thought I encourage you to have a look.
You’ll find a four main tools for project collaboration, contact management, chat and organizer/calendar. 37 Signals has more tools you might find useful as well.
John Jantsch of Duct Tape Marketing uses Basecamp and I know many others find this project collaboration tool useful as well.
I’ve recently used Google’s hosted spreadsheet for a “poor man’s” collaboration tool. It works quite well.