The JiWire search engine supports dozens of countries and indexes both free and paid hotspots. Search by street address, airport code, postal code or name SSID of the access point. Alternatively, browse listings by business type (e.g., airport, hotel and cafe).
Several other popular Wi-Fi hotspot online listings are powered by the JiWire database
The Wi-Fi ZONE Finder is a an official service of the Wi-Fi Alliance. This directory indexes only hotspot providers that have registered for the ZONE program. Such a certification system helps keep inactive hotspots, or hotspots of lesser quality, out of the index.
This directory is geared toward free hotspots. (Some of these otherwise free locations may require a store purchase, however.) Worldwide listings are organized both geographically and by business type.
Hotspot Haven offers a large directory with clickable maps. Search by address and by service provider. A user rating service allows customers to score and rank the quality of these hotspots.
WiFinder is privately held company that indexes hotspots worldwide. WiFinder can be searched by location and by protocol type (e.g., 802.11b or 802.11g). WiFinder lists fewer total hotspots than some competitive services, but it may contain some entries that other services do not.
source: about.com