Choiceofgames - They have a good active community, though their writing program is more code based. I find it simpler to write on this site haha. They have some good games too, and they have a few good ones WIP.
Project AON http://www.projectaon.org/en/Main/Home - Has most of the LoneWolf CYOA books and all of them are published there with the author's permission. I grew up playing those games and I highly recommend them. The later ones in particular were good. The first book is awful in comparison so it's worth sticking with it.
Otherwise there's other sorts of sites that cater to Visual Novels (similar concept) such as RenPy and various others I won't put down because plenty of them are NSFW but you could always check the VisualNovel Database if it takes your curiosity. :)
