The CD that came with your Palm organizer included both Mac and Windows versions of this calendar/address book/to-do list/notepad program. Put another way, if you have a Palm, you probably already have Palm Desktop for Mac OS X.
But you don't have to buy a Palm to enjoy Palm Desktop's power, good looks, and amazing variety of printing options. You're welcome to use it as a standalone information manager. (It's a free download from www.palm.com/support/Macintosh.)