In Development: UltraNano USB Development Board
The UltraNano is intended to be the ultimate USB Dongle development board. Based around the respectable PIC32MX270F256B microcontroller it has a built in USB A tongue connector. 0.1" pitch headers down either side with all the major protocols (I²C, SPI, UART, etc) available allow you to connect all your sensors and interface devices simply.
And you can't get much smaller, either. At just 18mm wide and 40mm long including the USB A tongue it is literally a USB dongle.
Programming is through the chipKIT STK500V2 bootloader activated either by the 1200-baud open/close of a CDC/ACM port (if you enable one) or the pressing of the USER button. It uses our FastProg system for simplicity of use, which can be disabled by the removal of a single 0603 capacitor (it is undecided yet whether that will be populated by default or not). Without FastProg the USER and RESET buttons have to be pressed together in the right way, but it does allow the USER button to be used for other purposes.
There is also one user controlled LED for you to indicate status with. PWM can be routed to that LED using the PIC32 PPS system, so you can even make it throb gently.
The UltraNano is currently in the prototyping stage and some videos of it in action will be forthcoming as soon as the next round or prototypes arrive on our desks.