Previously this was done through a Asus WL500GP access point connected to the ethernet port on the pi. At some point the access point died.
The plan is to "simplify" the setup by using a small USB-dongle 802.11 interface, and run hostapd on the pi.
See: http://jenssegers.be/blog/43/Realtek-RTL8188-based-access-point-on-Raspberry-Pi
On-board wifi is currently not operational.