We recently bought a big pile of very cheap AVR Minimus 32 USB dev boards via Manchester Hackspace.
These ship with a DFU bootloader. This works fine when building regular C code, but that involves a fair learning curve for people new to embedded development.
To that end I implemented Arduino support for the Minimus. This is now available on github. An AVR-ISP programmer (or Arduino pretending to be one) is required to replace the bootloader, but after that ‘s just as easy to use as any other Arduino board.
We have spare Minimus boards for sale at the space. We’ll even flash the Arduino bootloader at no extra cost :-)