Foursquare has shaken things up in the last few years. They've seperated out the discovery and gaming features into two different apps now. Foursquare is now a place/ratings discovery app (a'la Yelp) and Swarm is their gamefication app (edit), and as /u/musiquexcoeur pointed out, that's where Mayors live now.
I originally wasn't that fond of it, but as both apps mature, I've grown to really like both apps. And, if you're in FS, there's a button to take you to Swarm to check in now. Not necessarily a one stop solution, but it helps.
Here're the links for Swarm: Swarm for iOS Swarm for Android
And before somebody questions them, they were made by one of the designers at foursquare, I asked on twitter if they could knock together some foursquare wallpapers and they did https://twitter.com/#!/Mari18/status/111100542524198912