Although I'll refrain from obscure approximations regarding Tampa's metro/city population (and I'll leave out all the exclamation points too), that city is definitely up and coming in Florida. It's working on plans to build up it's downtown with more infill projects and it's also collaborating a regional effort to improve transportation.
Another Florida city that comes to mind is Orlando. Yes, we all know it's well established tourism sector. However, the city is making great strides in the high tech & manufacturing industries. It too is also involved in regional efforts to improve transporation through commuter/light rail efforts and infill development projects.
Outside of Florida, I'd have to wager Austin, TX with it's young population and impressive job growth, Charleston, SC, and Raliegh, NC.