Atmel's ATMega328P 8-Bit Processor in 28 pin DIP package. It's like the ATmega168, with double the flash space. 32K of program space. 23 I/O lines, 6 of which are channels for the 10-bit ADC. Runs up to 20MHz with external crystal. Package can be programmed in circuit. 1.8V to 5V operating voltage!

Note : These now include a 16MHz crystal with 2 22pf Capacitors. These will be shipped from 25th January 2013.

Documents:

• Atmel Datasheets
• Low Power Mode Tutorial