I stumbled across an interesting IPhone app called dot11wavelength by The Perseus Group @ www.wirelessfabric.com. This app displays the on channel frequencies for the
different 802.11a (5GHz) and 802.11g (2.4GHz) channels.
This app is helpful if you need the exact frequency for a channel in the field or if you are studying for your CWNA exam. They just updated the APP to include other country channel frequencies (JP,ES,IT, DE and FR).