Many people start out on canonfic, but my first fanfic was Wide Awake. For awhile, I only read AH because I wanted to separate fanfiction from canon. After awhile, though, I wanted read about vampires again & my first AU fic was Just Let Me Die. It was also the first fanfiction I read with non-canon couples. It's taken my awhile to accept Vamp AU because I was a firm believer in keeping an author's mythology intact, but I'm starting to warm up to the idea. I just started Dusk and Her Embrace--it's new with only one chapter, but I can tell it's going to be good.
There are other worthy stories that I don't mention here, but I only had room on the chart for 3 per category. Check out The Lazy Yet Discerning Ficster for really good recs, especially if you're wary of ficdiving (scrounging through fanfiction sites for fics without them being rec'd first by a trusted source). Another good place to go is FanFicAholics Anon - Where Obsession Never Sleeps! on Facebook and the C2 that contains all the group members' fics. It's a very friendly group & all fanfiction fans are welcome. Most of the recs & member fics are TwiFic, but there's also fanfictions from other fandoms. Everyone is very welcoming and there's almost always someone lurking in the group to chat and help out with any fic-related questions you have. TLYDF also has done a fandom-hopping article or two where they talk about other fandoms they are a part of and rec some of their favorite fics from them.
I hope this guide helped someone sift through the sometimes-confusing world of fanfiction.
TTFN--ta ta for now! I'll be updating this blog more now that I know someone out there is readin it. :)