Austria's Metronet continues to expand international roaming for its hot spot network -- by the megabyte: This is one of the most interesting of the roaming models I've seen. Metronet operates 300 hot spots in Austria, and has roaming agreements now that give its users access to 1,200 locations throughout Europe and elsewhere, including its most recent partners, SoneraHomerun (Finland), megabeam (Italy), Kubiwirless (Spain), and VEX (Argentina).
While it's a single account login for its users on all of the roaming networks -- which they expect will exceed 2,000 locations by year's end -- there's a per-megabyte fee of 70 European cents or 1 Euro, depending on your plan. Metronet also offers a PPTP-based VPN service for its customers.