PalmOne has a bunch of pretty good models. You can get them with built-in WiFi (Airport), Bluetooth, digital cameras, etc. in various combinations depending on how much you want to spend. Good models range from $200 (Tungsten E) to $400 (T3).
Sony's Palm-based PDAs are, in my opinion, not the greatest but some people swear by them. I've always found their hardware design to be clunky, and I don't like proprietary storage media (MemoryStick).
Tapwave's Zodiac is a good choice if you plan on doing a lot of gaming. It's also a really full-featured Palm for $300.
Note that you'll need Missing Sync from
www.markspace.com to sync a Sony or Tapwave device with a Mac. Palms, for now, work with Palm Desktop and/or iSync/iCal/Address Book, but future models (I suppose later this year) will also require Missing Sync.
Places like
www.palminfocenter.com ,
www.the-gadgeteer.com , and electronics.cnet.com have pretty good, in-depth reviews of various models.
The key question is what you want to do with it, though.