Guitar Shed 2, is the $18 shareware guitar suite for Mac and Windows. It's got too many cool features to list: a metronome, a chord library, a chromatic guitar tuner, a tab organizer, and other more. It's makers, Astoundit, say Seal uses it, so it must be good.

The second bit is Audio Hijack Pro, the venerable $32 Mac audio capture package, revved to version 2.6. This package allows you to capture audio from any application--digitally and losslessly--and save it in the format of your choice. Very cool, especially if you're trying to figure out an easy method of defeating iTunes' copy protection scheme or recording an Internet radio station.