I found it is a cheap and convenient piece of hardware to play with the V-USB firmware. It has two LEDs for quick firmware test. Most have 4 data lines, and some has 6 data line. I connect a JP to a spare pin of the header, which gives me 7th data line. To give up the VCC output, I solder a LED pin to VCC output pin, and this gives 8th data line. So I made a simple 8-bit TTL output device. With less lines, I made a 5-key USB keyboard based on the HIDKeys example. One of JPs is an ADC pin, so I also played with ADC function. To conveniently change firmware for different devices, I use slightly modified bootloadHID, so firmware can be updated without disconnecting the device from computer. The hardware is very reliable, so if it doesn't enumerate, it must be the firmware problem. This greatly simplify the debug procedure. However, for those who like to play with the hardware, this is not your option
Here is a link for the one with 6 data lines connected to the 10-pin header: http://www.ebay.com/itm/USB-ISP-ASP-Pro ... 3f18c641f7
It is less than $4. If you have patience to bid, you may get one with ~$2. There are other options (search usb avr isp), but most have only 4 data lines, and 4 pins are connected GND, which makes it harder to use those pins . Some has less JPs (normally 3), which may reduce the flexibility.
If anyone likes to play with it, I am glad to provide more information, such as jumping into bootloadHID for firmware update, etc.
I really enjoy the flexibility of V-USB! Thanks to Christian for the development!
-Xiangrui