There have been many things written about contradancing around the net. Here are a couple of good places to start:

What is contradancing?

An explanation by a Charlottesville dancer

Also, just type "contradance" into Google!

Here are some lists of contradances, musicians, callers, and music:

Great Meadow Music has lots of CDs
Dwayne Johnson's Contra dance locator
Ted Crane's DanceDB
More Links
Lots of info on dances, bands, callers, and articles about contradancing
CDSS has Summer programs scheduled (Pinewoods, Buffalo Gap, and Ogontz.)
Ashokan has summer Fiddle and Dance camps. The Augusta Heritage Center at Davis & Elkins college in Elkins, WV sponsors many great traditional dance weeks
The Swannanoa Gathering is a series of week long programs held in July and Aug at Warren Wilson College in Asheville, NC.