I'm writing my first app in Cocoa at the moment... aside from some shell scripts, this will be the first thing I've coded in years, and Cocoa is proving surprisingly easy and versatile. Long live Cocoa. BOH!
Anyhoo it's called Music Theory, and it comprises two tests to check your music theory knowledge, one on intervals and one on modes. I started by taking a music theory app written by my friend Will and rewriting it in Cocoa (its old-school Toolbox C). Great learning experience.
When it's done (far from it at the moment) and debugged, I will of course be posting my lil' freeware goodie ;]