Aside from live performance, recorded films of dance are possibly the most informative sources for becoming familiar with various dance styles and aesthetics. Remember that these are usually highly edited and produced and may not be representative of what happened on stage.
An excellent guide for getting to know dance styles through online resources is:
These library subscription and free databases allow access and information about all kinds of recorded dance. The three subscription services, Dance in Video, Digital Theatre+, and Medici.TV have many videos that you cannot find for free online.
There are many DVDs of dance performance at Campbell Library in both the general DVD section on the first floor, and in the DVD section of the Performing Arts Collection. Make sure to check Library Search to see which location it is in. You can browse dance DVDs under the call numbers GV1580-1835.