This proto shield comes with a socket for wireless modules, such as the Digi XBee, and a built in regulator and a big ol' prototyping area.
So, you wanna prototype, eh? With wireless stuff, eh? Well, you're in the right place. This shield will set you on your way, giving you the space you need to get your Arduino communicating without all them finicky wires. It's primarily based on Xbee modules, but any module with the same footprint will work as well (you can check out our entire range of wireless modules right here). The XBee modules, for example, can talk to each other from 100 feet away in indoors, or 300 feet away outdoors, but require line-of-sight. It's quite a distance, and a great way to developing a system for wireless communications.
The shield can also be employed as a serial/usb replacement. Alternatively, you can set a command mode that will let you use it for a range of broadcasting and mesh networking options. And, just because it is a protoshield after all, it breaks out each of the Xbee's pins to a through-hole solder pad for that extra bit of flexibility. This unit also has a switch that'll allow for control through USB or the microcontroller.
If you think an SD socket might be handy for some extra storage, check out this version.
You can take a gander at Arduino's official product page for more details and some application/usage notes.