You have to scroll to below the list of links that look like they're a footer, and you'll see a big blue bar that shows the 'where to buy' links. It sells for 50 bucks at Sparkfun, you can also buy the kit at makershed.
Hopefully they'll send some to Farnell so we Europeans can get a taste of it as well.
WLAN has been somewhat sorely lacking for these mini computers, your only option was pretty much the rather terrible MIPS platforms made for routers.