As part of a university course in Interactive Multimedia Design Andrew McCrum created this Google Maps mashup showing Wi-Fi hotspots in and around Belfast, Northern Ireland.
BelFi shows the location of free and paid Wi-Fi hotspots on a Google Map. The markers are colour-coded to show which spots are free and which spots need to be paid for. If you know of a Wi-Fi hotspot that isn't currently featured on the map you can submit the spot to BelFi.
There is a mobile version of the site at http://m.belfi.co.uk