Finding the right adapter for your particular tablet can be a challenge. Should you get a Serial or "PDA" adapter, an RS232 or 242, or a DB10 or DB9 plug...? And what about low price generic adapters? This page should help clear up any confusion you might have regarding adapters.
Serial model Wacom tablets come with one of two connectors:
Keyspan (now Tripplite) makes the best-supported USB to serial adapter for Mac OS X. TheKeyspan USA-28XG ($60-85) has two female Minidin-8 ports. I use this adapter for development, and it works very well with Wacom tablets. My only caveat is that it's very expensive! For PC-style Wacoms that come with a fat DB9 cable, theKeyspan USA-19HS (~$25-35) works well. However reports seem to indicate that it doesn't supply power to the tablet, so you should only use this adapter with externally-powered tablets.
Tripplite has posted drivers for all the Keyspan Serial adapters at these links:
TheBelkin F5U103 is a versatile USB-serial adapter with both a DB9 male and a Minidin-8 female port. Although Belkin doesn't provide a Mac OS X driver for this adapter, an open source Belkin F5U103 USB-serial adapter Mac driver is available. This driver has had issues in the past but recently some people have reported success with it. This adapter is almost as expensive as the Keyspan, so you may want something with better vendor support.
There are several inexpensive USB to serial adapters based on theProlific PL2303 bridge controller. Some adapters may supply power directly to the tablet while others require external power. Some vendors provide their own Mac OS X drivers, and Prolific provides a genericPL2303 Mac OS X driver. There is also an open source driver for the PL2303 USB-serial adapter, which some say is better than Prolific's. The originalSourceforge project seems to be abandoned, but there's anImproved Fork on GitHub intended for newer 32/64 bit systems that isdetailed in a blog post. Someone even made aconvenient package installer that should make things a bit easier.
Adapters based on the PL2303 include:
You can find more PL2303 information inthis MacOSXHints article.
There are also inexpensive adapters based onFTDI's FT232 controller series. Mac OS X drivers are available through individual hardware vendors, and also atFTDI's site andWiring Dot ORG.
Adapters based on FTDI chips include: