Hmm... While it's possible to run an ATMega328 on the internal 8MHz clock, it seems to be very inconsistent. Especially between different vendors. Looks like an external oscillator is going to be a requirement to avoid timing issues
Minimum wiring diagram for the ATMega1284, also on an external clock. It's quite similar to the 328 crystal hookup, with the pins being obviously different. I think the FTDI interface can be removed after programming. Should reduce power consumption even more
@th A chip in every rock and tree! :D