Looking for a hornpipe, polka, or gavotte? http://archive.folx.org/ is an online database of traditional and folk music. Find recordings, videos, sheet music, and lots of other information on ethno music from (mostly) Europe.
Note: I personally have terrible memories of being forced to square dance in gym class. But looking back, I think that what bothered me most was that it was contextless: lining up in the gym and dancing for no reason at all was just stupid and made everyone self-conscious. Furthermore, if you managed to achieve any kind of facility with the steps, the bell was sure to ring! However, I’ve also been to events where there were live musicians and folk dances that were a tremendous amount of fun for everyone. So I think the context matters a great deal for your average student.
If you’re teaching American history, for example, why not have students watch a musical movie such as “Oklahoma” in preparation, discuss what people then needed to do to prepare for a dance, and then plan your own? Let them dress up or play instruments, and then let the jam session continue from there!