For long distance shots I can definitely recommend Motorola Canopy wireless.
They come in a variety of frequencies, all proprietary links though, so
you'll need the AP and client radios. Very pricy, I might add, but terribly
I have a lot of experience with the 900 MHz series; they'll do 40+ miles
reliably on line of sight, 13 dbi antenna at the client and 10 dbi omni at
the tower. I have no doubt the 2.4 and 5.8 will do the 5 miles or whatever
they're claiming. I think they also have a new 5.4 GHz line which might get
a little less interference, depending on your environment.
On the 11g side, however, I've seen guys around here use a standard 200mW
atheros card attached to a panel @ 10dbi or whatever they're rated at. I
think they're using yagis at the tower though, no omnis that I know of.