Here are some photographs of a Worcester contra dance, courtesy Marty Miller and Gary Phillips. Click on the images for larger versions.
And below is a video of a contra dance in Wyoming, Ohio. It demonstrates the social aspect of contra: note that the young man in brown and woman in white stay together as what are called "partners", but the other people they are dancing with change every few minutes, with little to no repetition. By the end of the evening, they'll have danced with practically everyone in the hall. Newcomers and veterans alike are welcome; this is the woman in white's second outing, and she moves like a pro! That's thanks in part to the excellent accompaniment of the live music and the caller calling the moves, both of which you can hear in the video's background.
Several videos of actual Worcester contra dances have been uploaded to YouTube over the years: