I don't know why I haven't linked to this one before -- probably because the image on the front page makes it look like a professionally made piece of gear, but the eDrum is decidedly a DIY project once you actually start reading the text. This thing has tons of channels (at least 22!), so you could have a whole raft of triggers (truly a kit of Peartian Proportions...). Well worth a look in to.

Oh, and there is a pcb available to purchase, but you do have to look around a bit to find it.