Ordnance Survey opens UK geographic maps and datasets

All the maps and datasets can be browsed here:

http://data.gov.uk/data/publicbody/Ordnance%2520Survey

Data includes postcode to GPS co-ordinates (http://data.gov.uk/dataset/os-code-point-open) and locations of all bus stops and train stations (http://data.gov.uk/dataset/naptan).