The LilyPad  is a microcontroller board designed for wearables and e-textiles. It can be sewn to fabric and similarly mounted power supplies, sensors and actuators with conductive thread. The board is based on the ATmega168V (the low-power version of the ATmega168) (datasheet) or the ATmega328V (datasheet). 

Summary

Warning: Don't power the LilyPad Arduino with more than 5.5 volts, or plug the power in backwards: you'll kill it.
Microcontroller    ATmega168V or ATmega328V
Operating Voltage    2.7-5.5 V
Input Voltage    2.7-5.5 V
Digital I/O Pins    14 (of which 6 provide PWM output)
Analog Input Pins    6
DC Current per I/O Pin    40 mA
Flash Memory    16 KB (of which 2 KB used by bootloader)
SRAM    1 KB
EEPROM    512 bytes
Clock Speed    8 MHz

Programming

The LilyPad Arduino can be programmed with the Arduino software (download). *Note*, the LilyPad Arduino should only be programmed with software versions 0010 or higher. You can program it with earlier versions, but all of the time related functions will be off (twice as slow as they should be).

The ATmega168V or ATmega328V on the Arduino LilyPad comes preburned with a bootloader that allows you to upload new code to it with the Arduino software. You can also bypass the bootloader and program the ATmega through the ICSP (In-Circuit Serial Programming) header; see these instructions for details.

Power

The LilyPad Arduino can be powered via the USB connection or with an external power supply.

If an external power supply is used, it should provide between 2.7 and 5.5 volts. This can come either from an AC-to-DC adapter (wall-wart) or battery. Again, don't power the LilyPad Arduino with more than 5.5 volts, or plug the power in backwards: you'll kill it.

Physical Characteristics

The LilyPad Arduino is a circle, approximately 50mm (2") in diameter. The board itself is .8mm (1/32") thick (approximately 3mm (1/8") where electronics are attached).

Washability

Wash at your own risk, recommended washing projects by hand with a mild detergent. Drip dry. Make sure you remove your power supply first!