New AVRopendous models
One product very similar to the Teensy USB development board are the open-source (hardware and software) avropendous boards, which now seem to be available in a DIP form factor ala the Teensy board, at a similarly low price. The AVRopendous-DIP ($22) uses the same AT90USB162 as the Teensy board, and allows selecting 5v or 3v3 [...]