Continue your search; go to WorldCat Discovery, the library catalog. In WorldCat Discovery type in the keyword "dance" and, on the left-hand side, select "video" under (show more) format.
You may also search on an individual dance type or a particular choreographers name.
YouTube is a good place to look for visual lessons and online performances. Keywords such as "dance" followed by the type of dance, such as Pavane, jitterbug, etc., will yield online performances, lessons and explanations. Using "dance therapy" will show dance therapy sessions in a variety of settings.
Evaluate sites the way you would evaluate a book or other resource. Who sponsors it? When was it last updated? Who videotaped it? Who points to it?