ISP offers wireless on Boston's South Shore: a reader of this site sent in his firm's URL and answered a number of questions. The systems that this firm is using rely on 802.11b-like networking nodes that use their own encoding algorithms. Customers must use client adapters provided by the firm. Install costs are around $400; monthly service ranges from $50/month for residential to $500/month for business T1-like service.
They have a 500-foot tower mount, allowing them line-of-sight access to quite a lot of nearby residents. They have the option to employ a variety of hardware and software solutions to overlap service, which they offer at speeds of a few hundred K up to 6 Mbps. Because they're using proprietary equipment, they can control speed, access, etc., in a much more secure manner than plain old 802.11b. They're also offering VPN service.
I'd like to write more about ISPs around the U.S. and the whole world who are offering for-fee networks like this. The free networking movement is terrific, and I love it, but as I've spoken about with members of various groups, free networking doesn't have QOS (quality of service) as its primary goal. Free networks will be a great supplement, complement, and partner to for-fee networks, especially in dense population centers.