Other European rollouts, including a Paris debut, are expected soon. We also saw on the Foursquare Twitter account that the service is expanding to college town Chapel Hill, NC. Currently, the popular location-based app is doling out Shameless Drunkard and similar badges in Amsterdam and a collection of large U.S. markets.
Right now, Foursquare-enabled U.S. cities include Atlanta, Austin, Boston, Chicago, Dallas/Fort Worth, Denver, Detroit, Houston, Las Vegas, Los Angeles, Miami, Minneapolis/St. Paul, New York City, Philadelphia, Phoenix, Portland, San Diego, San Francisco, Seattle, and Washington, D.C.
Interestingly, although we don't see this city on the list, we've also noticed quite a few Boulder, CO Foursquare updates and oustings, mostly during and in the aftermath of Andrew Hyde's Boco music/food/geekfest. These spots seem to be showing up on the site as part of Denver.
Curious persons in as-yet-Foursquare-free areas should follow Foursquare's Twitter account for cryptic responses and late-night updates on where the app and its bar-hopping advocacy will land next. The company is also seeking mobile beta testers for several devices; interested parties can apply here.