Zigbee starter kit, any suggestions?
Digi's online store has an XBee 802.15.4 Starter Kit that includes:


  
  (2) XBee 802.15.4 w/ Wire Antenna
  (1) RS-232 Development Board
  (1) USB Development Board
  (1) RS-232 Serial Cable
  (1) USB Cable
  (1) Power Adapter
  (1) 9V Battery Clip
  (3) Adapters
  


This kit will not only let you start talking with the XBee modules, but actually program them as well.You can see a complete review of the kit from The ZigBee Project blog.

There's also a more basic kit XBee Wireless Communication Starter Kit at Trossen Robotics:


  
  [2x] XBee 1mW Communication Module
  XBee Explorer USB
  XBee Explorer Regulated
  A to Mini B USB Cable
  


And as always, you can pick up individual modules, Arduino shields, and accessories at SparkFun.com.