Dfrobot Xbee Usb Adapter V2.0, Atmega8u2 Usb To Ttl Compatible With All Xbee, Bluetooth Bee, Zigbee, Wpm Wireless Programming - Demo Board - AliExpress
Amazon.com: SainSmart XBee USB Adapter for Arduino UNO MEGA R3 Mega2560 Duemilanove Nano Robot : Electronics
UART-Serial-USB : USB Serial Light Adapter Atmega8U2 Arduino ...