The Parallax StampWorks Experimenter Kit is a comprehensive collection of everything you will need to learn about efficient embedded design. This is a great package for those who want ALL the accessories!
Looking for 802.15.4 Zigbee-like device with smarts? XBee with more features? Check out Synapse modules! Small, low-power, 2.4 GHz plug-in transmitter-receiver modules, with an extended range up to three miles and power consumption as low as 2.5uA.