My knowledge is a few years old, but here goes:
In the past, there was no uniform system of hand-to-hand combat training for Navy SEALS. They contracted with several different instructors on a temporary basis. The result was that a number of different "official" courses were marketed to the public.
I have some experience with (*cough* bought the tapes *cough*) two of them. For background, I have third degree black belt in Taekwondo and trained a bit with kickboxers in my youth, but have always felt that there were weaknesses in real-world applications.
The most hyped version was marketed by Jerry Peterson. He called it Hostile Control Systems. (The "official" version was called "SCARS.") It was apparently offered at BUD/S for a limited period of time. It is a take-off from San Soo kung fu, and the "unique" part of the program was what he called autokinematics -- if I hit you in a particular spot, you will react by doing a predictable movement, allowing me to anticipate and set up my next technique. That's a nice theory, but it has its practical limitations. Let's just say that I regret having spent the money.
The other instructor who got into the SEAL H-2-H business was Paul Vunak. His stuff is based on jeet kune do, and in my view is much more practical. One of Vunak's trainees, Frank Cucci, has also marketed a series of tapes. There is no substitute for real instruction, but if you already have a strong background in martial arts, there is some useful knowledge in either Vunak's or Cucci's series. They are, I think, still available from Threat Response Systems. Vunak also markets DVD's in Black Belt Magazine.
I have heard that the SEAL's have taken this in-house now, but I couldn't tell you for sure.