This is a USB Host Shield v2.0 by Circuits@Home. The shield can turn your Arduino into a USB host, allowing it to connect to a plethora of USB devices, including keyboards, game controllers, USB drives, Android phones and more. A list of supported device types from the Circuits@Home product page follows.

The following device classes are currently supported by the shield:

• HID devices, such as keyboards, mice, joysticks, etc.
• game controllers – Sony PS3, Nintendo Wii, Xbox360
• USB to serial converters – FTDI, PL-2303, ACM, as well as certain cell phones and GPS receivers
• ADK-capable Android phones and tables
• Digital cameras – Canon EOS, Powershot, Nikon DSLRs and P&S, as well as generic PTP
• Mass storage devices, such as USB sticks, memory card readers, external hard drives
• Bluetooth dongles

I used this board for a project back in school but haven't touched it since then. The jumpers for the SS and INT pins were cut and rewired for the project, but otherwise the board has no outstanding modifications or issues.