It's full speed ahead in Charlotte:
The Charlotte Regional Visitors Authority board unanimously supported making a formal bid for the convention later this year, soliciting a request for proposal and formally declaring the city’s interest to party leaders.
Mayor Anthony Foxx will lobby for the event for the public sector, while Duke Energy Chief Executive Jim Rogers will lead the private fund-raising campaign. To host, Charlotte will need to raise $50 million, organizers say.
Mayor Pro Tem Susan Burgess has been pushing for a Charlotte campaign for months. Burgess, a member of the national party, distributed buttons and posters last year, stirring interest among Democrats. The pitch for Charlotte will include North Carolina’s support of President Obama in 2008, making him the first Democratic presidential candidate to win the state in 32 years.
I think Charlotte remains the front-runner for the convention, purely based on the state's political significance.
While there are probably several cities in the mix that we don't know about here is a list of those we do know are interested:
Charlotte, Philadelphia, Phoenix
Phoenix, Salt Lake City, Tampa Bay
2012 Democratic National Convention Site Selection News
2012 Republican National Convention Site Selection News