I know what you mean, I often feel exhausted with the Harry Potter fandom, too. I try to limit my time spent with the fandom so that I still enjoy it occasionally.

Unfortunately, I can't really recommend new fandoms to you. I have the same problem with TV series fandoms, I don't follow them closely enough. Yet at the same time, I'd really like to read some good Grey's Anatomy or Gilmore Girls fanfiction for once, if you are so inclined... Book or movie-wise, nothing comes to my mind right now. But maybe I'll think of something later...