I'm on a couple of different GSD boards - I'm a moderator on the one that Liesje is on. I joined 4-1/2 years ago, and I really like it. It's a pretty active board, with a diverse international group. It covers the gamut, from ordinary pet owners to people active in obedience, rally, agility, Schutzhund, and other sports. There are SAR people, law enforcement people, disabled people with service dogs, people with therapy dogs, you name it. Also, some very experienced people on a wide variety of health and nutrition topics, and it's really active in breed rescue too. Oh, and lots of pictures!
I like this board a lot too. The behavior and training topics are particularly interesting, with a variety of opinions, and some very knowledgeable people participating in some great discussions.