Map of Towns within each state

[Tinkerers]

Hi,

I'm a programmer looking for a way to display a map image of a state, such as Massachusetts on a web site. The State should display each town and it's boundaries and allow me the ability to background color each town programtetically.

In other words, I may wish to color the town of Sprinfield Blue and the town of Ludlow Green. Each time, I display the map I may wish to background color different towns. I need an easy and free method to do this. I see all sorts of map making software out there, but nothing specific to the above requirements

Any ideas?
Thanks,
Paul