I've found the forum "Help! I'm Looking For..." which allows you to request story recommendations from other Harry Potter fans to be a good resource. It's a sub-forum of the Harry Potter fanfic site called FictionAlley, and people post there quite frequently.
http://forums.fictionalley.org/park/...?s=&forumid=19
There's also a sticky on that forum that has several recommendations for various Harry Potter archives.
http://forums.fictionalley.org/park/...hreadid=137438