So a friend suggested that I should build a contact mic out of a pizeo disc speaker. So, built me one of these pre-amp circuits last Thursday: http://www.hawestv.com/amp_projects/fet_preamp/fetpreamp1.htm
Shown here is an earlier version, I later added a longer, thinner wire between the disc and the preamp, so the disc could be silly puttied to something without the amp getting in the way. Works really well! My prior experience with analogue semiconductor use had left me expecting a tempermental, finicky result, but it turned out ok! It's really great for picking up the shuffling noises of lentils tumbling in Tupperware.