Inspired by Romilly's veroduino but requiring some hand-holding to get me started, I happened upon Oomlout's Component Bundle for Arduino Compatible --- I already had some breadboard lying around. While I was there I picked up a USB-Serial cable (which you need in order to actually program the thing).
Having assembled the kit by following the instructions for the BBAC (hint: you can use plain wire instead of 0-ohm resistors!) and tested that it was working (mostly: the cable is too heavy for the serial port header on the breadboard, it kept pulling it loose, making it next to impossible to download sketches), I decided that the thing would need a permanent home: stripboard (or veroboard as it used to be called).
Here are the bits required for a minimal development board:
Once you have this wired up, your breadboard is freed-up for actual experimentation!
The board assembled: