I just got back my boards for an ISP programming helper for doing Arduino on a breadboard. It is designed to sit over top of the ATmega168/328 in a breadboard and provides the 6-pin programming header. In addition, it has the Arduino pin mapping information on the silkscreen to ease wiring.
Some obvious extensions I can think of are adding the non-pop pads for a ceramic resonator to the bottom side, and possibly the reset line. They’d have to be SMT, since there isn’t really any more room on the top side when a shrouded connector is populated.