The Leaky Cauldron - the best place to find Potter-related news of any sort
JKRowling.com - sometimes she inserts clues and explains things you won't be seeing in the books
The Harry Potter Lexicon - pretty much the definitive online research resource for the series itself
This was my very first online fandom, though I wrote many, many Redwall spinoffs from about age seven to thirteen, one of which you can find at my FanFiction.Net profile, along with all the rest of my Harry Potter works. All of these contain spoilers for Books I-IV, although the names and events were all made up before the release of Order of the Phoenix.
Impossible Things - Azkaban does funny things to a man's head, but even in that place, there are occurrences which simply cannot be.
AprËs le DÈluge - Viktor Krum has a choice to make after the Third Task.
Decoration Day - Sirius Black finally gets his chance to pay homage to fallen friends.
Uncle Algie Makes A Call - or, Neville Longbottom Remembers The Events Which Precipitate Why He Merits A Toad
Prongs Rides Again - James Potter was not, contrary to popular knowledge, lost in a flash of green light that fateful Halloween night. Thirteen years after being torn from his body, he now has a new mission ahead of him. But which will be the greater task - defeating the newly-risen Dark Lord, or convincing his son he is no longer and orphan? Eight chapters plus an epilogue.