I've never had any trouble getting any printer to work with my Mac. You're probably fine whatever you buy (assuming it's got a USB interface, of course). If you're nervous, though, do any one of these three things:
Option 1. Look at the online store at apple.com. Find a printer that looks good to you. Write down the model number. Go somewhere else and buy it cheaper.
Option 2. Look for the something on the box that says "Mac-compatible."
Option 3. Pick out a printer that looks like a good deal. Go to the manufacturer's website, and then to the drivers section. See if they have a Mac download for that printer.
Don't sweat this. You're not going to have any trouble.
EDIT: just realized that this thread is way old, and therefore you've already done it. Ah well.