I had this circuit board made by BatchPBC just before the closed down operations. It is a very simple board consisting of a FTDI FT232RL USB to Serial Converter chip, a mini USB jack, and some header pins. I had this board made so I could easily interface with other circuitry I was builing that I didn't want to put a full serial output on but still wanted to see debug data. I connected this to my Waveform Generator, USBMRF, and most recently the GPS Module I was testing. It provides a 5 Volt output for powering connected devices. The signal voltages are 3.3V.
Here is the board I got from OSHPark. Unfortunatly I scrached it up a bit soldering on the parts but I do love the purple color and gold plated pins. Works fine too.
The schematics for this board are available on my SVN at:
It was designed using gEDA tools and PCB. I also have the design shared on OSH Park:http://oshpark.com/shared_projects/kFZ6bvyL