So far I've identified 9 different pinouts (when chosen the "easiest" type of chip, i.e. soic rather than tssop or tqfp rather than qfn) for where the power, usb and iscp pins are located.https://docs.google.com/spreadsheet/ccc ... 0SkE#gid=0
I'm not done yet so a few more variants are bound to pop up.
I did a quick version with a 5x5cm base board, where the daughter boards (with up to four different PICs on each daugherboard) plug in at the top, two iscp connectors (5 & 3.3 volt) at the right, usb and a connector for a Bus Pirate LCD adapter on the left sides. The three connections going to the LCD are also brought out to three LEDs if the LCD is not required for debugging.