I make my own, haven't bought one in several years.
www.crossroadsfencing.com/BobuinoRev17
Parts sources:
blank uCs from mouser, they generally have the best price
digikey.com,
dipmicro.com,
taydaelectronics.com,
avnet.com, (TPIC6B595s)
phoenixent.com,(connectors,wirewrapping - best if >$50 total)
arrow.com, (only source for some things, like AD595 ADC)
PCBs from iteadstudio.com, internationalcircuits.com
Sparkfun.com, gravitech.us, adafruit.com, nkcelectronics.com, pololu.com, mdfly.com for the occasional module in no particular order