I've created a new program for the Mac called CloneKeys. I mostly wrote it for myself, so I can multi-box on my Mac, but I'll probably release it to the public soon. I'll probably release it under the GPL (open source) and just ask for Donations from people that find it useful.

Basically, it's very similar to Keyclone for Windows, but coded from scratch for the Mac.

Here's a short demo movie of it in action:

http://files.filefront.com/clonekeys.../fileinfo.html