I burned a workalike board to use with my physical computing classes at RISD. It uses the FTDI USB to TTL serial cable so no serial chips are needed, and no current draw. It turns out to be really cheap with the Atmega chips about 2.50 from Digikey and most of the rest of the cost of the board is header pins and the chip socket, which we may just leave off.
Nothing on the web site yet - I'm getting ready for classes but I'll post the plans and Gerbers when I can get to it.
Just wanted to encourage people who want to do this - it's fairly easy. Programming the 168 fuses was a little confusing and daunting at first but it all feels easy after the first one or two. AVRdude wanted to see Tiger (10.4) on my mac so we used a PC and AVR studio (and lots of head scratching). I have screen shots I'll post somewhere so others will have a little more guidance.
The cost is an issue, but I like the idea of students being able to put together low-cost through-hole boards at their convenience when they need them. I'm hoping this will facilitate smaller one-off pieces to which students are sometimes reluctant to dedicate a $35 board - not to mention shipping.
Yes the cable does cost about $18 in quantity but then it's a one-time purchase. The board is also smaller and lighter - not having the comm. chips and all.
Plus there are some convenience features I've picked up over the years, such as a buses of positive and negative header pins adjacent to the analog pins that facilitate easy-to-hookup, polarity-keyed sensors. We just use four-position female .100 solder-tail headers for this. With a little hot glue, they make really robust convenient sensors.
Tell me where to send it and I'll email a screen shot of the layout.