Since I haven't visited here in FAR too long, I may be embarrassing myself by pointing you all toward a site that you already know about, but...
While doing a search for a Harry Potter timeline, I turned up "The Harry Potter Lexicon." Don't be fooled by the plain-Jane graphics, this site has got lots of good stuff. In addition to multiple timelines, it has truly interesting discussions on much of the series, and more. It's a thinking fan's fansite. Try it out: