As a rule, I try to avoid fanfics. Although some of them are really good, the majority of them... well, I don't like the majority of them. And I'm not completely sure that the ones that are any good are worth reading through the ones that aren't.
I do enjoy that the DC universe is able to change from time to time- killing Robins, rather than having MaryJane get back together with Peter- they were seperated, and supposed to get divorced, but that changes something, so she comes back and quits her job because she loves him so much. Awww... how... wait, that writing sucks!
Especially with Vertigo (DC's Indie line) they're free to do pretty much whatever they want. See "American Virgin" (which isn't any good, but interesting writing) and "Y: The Last Man" (incredibly good writing, interesting ideas, sub-par artwork) for reference.
-kv