If you are seeking skill enhancement here are some to check out:
Nigel Foster - series of 6 DVDs can be bought as a set or individually. I particularly like #3 Strokes and #4 Rescues
Ben Lawry - Ben Lawry's Forward Stroke
Ken Whiting - Rolling a whitewater kayak
Rolling a Seakayak
Gordon Brown - Seakayaking w. Gordon Brown
Grace Under Pressure - classic VCR/DVD on rolling
Rolling DVDs in addition to the ones above:
Eric Jackson - EJ's Rolling and Bracing
Jay Babina - First Roll
Dubside - the Greenland Roll
various instructors - the Kayak Roll
Ben Lawry - Dr.Ben's New and Improved Rolling Elixir
For free stuff made by knowledgeable people
paddlinginstructor.com (David Johnston's blog)
Derrick Mayoleth's blog 'Kayak Quixotica'
Keith Wikle's blog 'gokayaknow'
Helen Wilson's site (greenland style)
the Bloyd-Peshkins' blog
Websites for CASKA, BodyBoatBlade, Werner Paddles
paddling.net - on the home page there are articles by certified instructors, pix not vids unfortunately.
this is just a small but good sampling.
DVDs and vids are fine, but nothing takes the place of on the water instruction, be it w. an instructor, a club member, or very knowledgeable friend. Followed by a lot of practice.
For pure paddling fun there is a series called "This is the Sea" by Justine Curvengen. She is both paddler and filmmaker. She has a whole series going of different venues, daytrips, expeditions, etc. Her most recent release is a very lively one about canoeing, the rest are all about seakayaking.
I think if you check the online store of Seakayaker you'll find a number of DVDs. I feel OK mentioning that since I don't work for the zine.