SparkFun has a board
but if you read the comments there (and here) you'll see some people have problems using it with the RN-XV WiFly module. Cutting or replacing the diode seems to fix it.
Google says Amazon carries this
which looks like it's just this being resold for a higher price:
http://www.solarbotics.com/product/51835/
It looks like Mouser also carries that board, even cheaper still:
(disclaimer: I haven't used any of these boards. I do have the RN-XV WiFly board and it works great, but I use it on a breadboard with this: Breakout Board for XBee Module - BOB-08276 - SparkFun Electronics).