From those where I actively look for new updates:
- “Heather Potter_ After the War”
- “Harry Potter and the Annotated Story_ The Chamber of Secrets”
- “Harry Potter and the Ritual of Love's Memory”
- “Fair winds and following seas”
And one non-HP (yes, they are more snobbish and having the canon fully in public domain, most of stories are on the commercial sites):
- “The-Sailor_s-Rest-_-A-Pride-and-Don-Jacobson” … Pride & Prejudice meet Persuasion meet Horatio Hornblower, slightly too long and slightly failing on “Show, don’t tell” rule, but otherwise obviously professionally written thing.