From the MAKE Flickr pool:
Member Filmosity built this microphone to amplify a blues harp. He also made a minty amp to go with it – cool idea for portable playing.

I made this harmonica mic from scrounged pieces of other items. I got a $20 dynamic mic from Radio Shack and used the element and the windscreen. Also got a potentiometer (volume control) and a mono phono jack. Put them together using the bell from a garden hose sprayer ($8), part of the column from the mic, and a Listerine bottle cap. The mic fits nicely in the hand with a harp in my hand. Not too heavy, not too light. Unfortunately, it seems I wired the potentiometer incorrectly, so it doesn’t actually do anything. On version 2.0 I’ll wire the pot correctly, and use 2 listerine caps for extra room.

Don’t sweat that potentiometer, mistakes are still the best way to learn! -Link

Related:

Build an I-Mic -Link