AT&T runs one of the largest Wi-Fi networks in the US - thousands of FreedomLink locations (operated by Wayport) made up of UPS Stores, Barnes and Noble, Caribou Coffee, various airports, and McDonalds hot spots. Currently AT&T offers hot spot access for $1.99 per month to DSL customers - less than Cingular and a lot less than T-Mobile. Add cellular wireless data to the mix and things start to get interesting.

With Cingular offering UMTS nationwide and HSDPA in certain markets,
the combination of real 3G speeds, Wi-Fi hotspots, and voice could be a
winning bundle over Sprint Nextel, T-Mobile, and Verizon deals. Sprint
and Verizon lack good add-on plans for Wi-Fi, although Sprint has a
roaming network of nearly 30,000 locations worldwide—they just don’t
bundle it well and domestic locations are largely FreedomLink’s.
T-Mobile has a great inclusive network in the US and roaming deals
(single login, single bill, but fees) worldwide, but they don’t have a
3G cell network.

As a Cingular customer, I'd gladly add a couple bucks to my cell phone bill for bundled FreedomLink access.