Yes, for some reason S2 has never had the cult following like other manufacturers. Probably because other than the 7.9 or 9.1, they never really had a "classic" boat so to speak which attracted a lot of attention.
I don't think the fact that they stopped making boats after 1987 matters - Tanzer had a very active following and their class association provides lots of info about the boat.
Bret's site is a good start - I have sent him a brochure on the S2 - I own -the S2 27 - you'll find next to NOTHING on that model - they only made 85 of them from 1985-1987.
If you have a 7.9 - they have an active web site so to speak, the 9.1 forum is fairly inactive. At the end of the day, the larger the sales volume, the greater the odds you'll find information and an active web presence.
I do look forward to see what GOB has to say about S2 - I am sure they'll provide some history about Slikkers, etc. I also hope they can interview Scott Graham and/or Eric Schlegeter who designed the racing S2 boats (and the 27 performance cruiser).