The Real Bare Bones Board by Modern Device is a neat little Arduino clone (it was my inspiration for the JeeNode, in fact). The RBBB is easy to build, very small, and very popular, at JeeLabs as well.
Now, there’s also a ready-made “pre-assembled” 5V model, based on the SMD version of the ATmega328 which has two additional analog-in pins (note that they are not general purpose I/O pins!):
Well labeled for use either way, and very convenient for breadboard use. Here’s the bottom view:
The headers and DC power connector are included, but not soldered on – for maximum flexibility:
Fully compatible with the RBBB, but considerably flatter if you omit the DC connector.
I’ve added it to the JeeLabs shop and it’s available now. It’ll probably be used in future projects here as well.