Arduino Nano and clones
| ATmega328 (ATmega168 processor before v3.0) | 1.70 in × 0.73 in [ 43.18 mm × 18.54 mm ] | micro-USB | 16MHz frequency | FTDI | FT232R | 5V power | 16/32kb flash | 0.5/1kb eeprom | 1/2kb SRAM | 14 Digital I/O Pins | 6 I/O Pins with PWM | 8 Analog Pins
This small USB-powered version of the Arduino uses a surface-mounted processor.
When purchasing for use with a RepRap it will be useful to make sure you obtain one with a micro-usb, and with 328 (version 3) processor
Cost: ebay, clone: 2Euros/US$