I'll update this post periodically. Sometime (this summer?) I'll plan an electronics swap meet at the HF but for now:

3.3V usb to serial cables, works just like a ftdi cable but uses a pl2303 chip (drivers). You'll have to hack your own connector onto the end. There's 4 wires, +3.3v, GND, Tx, and Rx. If you don't need +3.3v a standard 3mm audio jack works great for Rx, Tx, and GND. $4 each (3 remaining)