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.