Here's some really nifty shareware goods. First, the tuner, called Chromatic Tuner 1.3, is a very simple but elegant guitar tuner for OS X. Next, a piece of software for training the musician's ear--basically, it's a piece of training software for identifying chords, notes, and rhythmic patterns. This package, called Dolce ear training, might be a useful addition to your arsenal if you're a music student.

Finally, be sure to check out Scrambled Hackz, a program that can transform human beat box into actual music sequences based on a database of pre-recorded samples. Scrambled Hackz isn't available for download yet, but check the author's demonstration video it's interesting. He's planning on releasing the thing under the GPL license, which means it will be free and open source.