I made on a couple of months ago using a cigar box ($1), a piezo from Radioshack ($2) and a jack ($1). I put some foam rubber in the cigar box to give it a bit more bottom, stuck on rubber feet and I was good to go. Very easy to make and cheap. Sounds pretty good directly into the mixer and no feedback to speak of. Just make sure you use a box that's not too flimsy or too tall or you'll either crush it by putting your weight on it or your leg will get really tired from the steep angle. Bonus: if you don't already know, you'll find out whether you're left or right footed! ----------
