There are at least two different ukulele documentaries that have been produced in recent years: The Jumping Flea and Rock That Uke. Both of them are coming soon on DVD. Personally I'm more excited about Rock That Uke, since it appears to have interviews of more people. I've been keeping my eye on the DVD page at Elderly Instruments, waiting for it to appear. As of right now, it's supposed to be shipping at the end of January. But the date's changed several times over the past few months, so I'm not putting much credence into that date.
One documentary that is out right now is the PBS documentary "American Aloha: Hula Beyond Hawai`i", which is a fascinating look at some hula teachers on the mainland, and their separate approaches in teaching Hawaiian dance and how they adapt it. It's available at Netflix, and I'd definitely recommend it if you want to see some amazing Hawaiian dancing.
When the other two uke DVDs come out, I'm definitely going to have to have a viewing party at someone's house, and invite all the uke students from my class.