This would be an INCREDIBLE online business directory!

Been out of the loop for a while. Glad to see this place still smokin'!
Looking at homes and apartments for sale or rent, I came across this site:
www.hotpads.com
Go there, click on your area, and watch the map come to life (takes a few seconds for the interactive map to load). Available units pop up that can be clicked for further information. Just single-click on a building for options. If you double-click, half the screen is used for other data.
Wouldn't that be great for a map of your own town, but instead of showing available homes, it could show businesses, with clickable links that provide further details, coupons, videos, etc about the business?
The "about" page gives a clue as to how it's done, but that's still way over my head.
I tried looking for a pre-made software that might be available to mimic this, but might just have to get pricing from a programmer.
Any suggestions on where to start?