If you haven't read
'Make a Wish' by Rorschach's Blot yet, you need to.
'Poison Pen' by GenkaiFan is also pretty great.
'The Dark Lord's Equal' by Lens of Sanity is a pretty awesome time travel/fix-it with some AU. I find it pretty funny, but my humor is a bit odd.
'Mastermind Hunting' by Louis IX starts out with a simple question 'What if Dudley had died as a toddler?' and then turns into a huge epic.
'Dimension Hopping for Beginners' by nonjon is a good one for laughs.
'Almost a Squib' by BajaB explores that cunning side of Harry that so rarely gets attention by taking away almost all of his power from the beginning.
'The Serpent and the Mirror' by Paimpont is a nonmagical AU that is really well thought out. Dr. Dumbledore is Harry Potter's psychologist.
'Neville Longbottom Can Conjure Food From Nothing' by Norwegian Blue is also pretty sweet and funny.
Some of these get kinda heavy, like Mastermind Hunting, but nothing too bad and it's usually nothing related to the actual books. These are just some of my favorites.