Here's an (arguably) nifty musician tool: 4 tracks of recording for your iPod.
Now, I'm old enough to remember the days when the cool thing was a Teac 4-track reel-to-reel. If you had one of those in your home stereo or studio, you were really something. But now, that same functionality (and much more, actually) can be had in an iPod.
I dunno, there just seems to be something too convenient about humping a 4-track around with you all the time...
Sonoma Wire Works