The Optek Fretlight guitar now works with Apple's GarageBand software on the Macintosh through a new plug-in. The software is in beta and is free through May 15th.
Seems like a good trend with more guitar software being made compatible with the Macintosh. Line6's TonePort and WorkBench software are also Macintosh compatible, though GuitarPort is not. Seems like it should be though.