Herb Help!

On top of loving popcorn...I also love cooking with fresh herbs. But living in downtown DC makes having a garden a bit of a challenge. But considering how often I use rosemary, thyme, cilantro, mint (chocolate chip cookies... :) etc...I am beginning to think growing a window box of herbs might be worth a shot. And decorative!

There is a rather neglected, overgrown rosemary bush hidden behind some shrubs in front of our building...but I'm not sure who planted it (if they even still live here!) and fear I'd be pilfering some else's herbs!

Any green thumbs have recommendations on what to plant with what?? Any DC-ites have any recommendations on where to buy good quality, cheap herbs? Or cute little window boxes? All advice greatly appreciated...