KineticFlix is the only niche site we've come across that does only fitness, dance, and sport-related DVD rentals. It won't appeal to that many people, but if you work out and want some variety without having to purchase many DVDs, then it might work for you. KineticFlix was formed in September 2008 from the merger of Flickety Fit and Dancing Flix.
Reflecting this dual heritage, the site is starkly divided on the front page into Fitness/Sports DVDs and Dance DVDs; forcing you to make an additional click to actually browse the genres in those categories. A minor quibble, but it would be easier on the visitor to simply list the 14 dance genres and 17 sports/fitness genres all on the front page.
These genres include categories you'd expect like Aerobic/Step, Pilates, Weight Loss, Yoga, or for Dance, things like Ballroom, Ballet, Tap, Street, etc. The collections seem quite extensive, and you won't find such a wide coverage of these niche areas with any of the more general DVD rental services. If they don't have a fitness/dance-related title, just click Request a Product, and they'll endeavor to acquire it.
Some of their titles can also be purchased--you can tell if you see a Buy button as well as a Rent one. Keep in mind the titles are shipped from near the Continental Divide in Montana, and could easily take 2-4 days to reach most US locales.
The site is run by Linda Parker and Lois Schlyer.
Prices: KineticFlix has three unlimited online rental subscriptions: one disc out for $12.99, two discs out for $16.99, and three discs out for $20.99 per month. There are no free trials.