Think of the JeeNode as an Arduino + Xbee shield + Xbee, but smaller and less feature-full than the XBee.

The JeeNode is based on an Atmel ATmega328 - the same as an Arduino - and was inspired by Modern Device's Really Bare Bones Board, which is like a minimal implementation of an Arduino. The USB communication interface has been removed and any USB-to-TTLSerial based on the FTDI232R chip is guaranteed to work as connection. Being compatible with Arduino boards such as the Duemilanove means that you can use the IDE to upload a sketch using any PC running Windows, Mac OS X, or Linux.

The radio is a HopeRF wireless module, which is available for the 433, 868, or 915 MHz frequency bands. It is not compatible with the XBee - the RFM12B has its own very lightweight RF12 driver library.