I had no idea Foursquare's API had matured so much, loads of opportunities to build interesting things. This write up has some great insights into some of the challenges of implementing against it.
"Step one: matching up the venues" - for your interest Bopgig uses a Google search on foursquare.com to obtain venues, seems to work decently and is automated. The 4sq api seemed to return too many errors when last tested.