Not a member, but I'm excited for this possibility.
I found out about this via the sci-fi book club I joined mid last year, and it's actually really cool if you read a lot of sci-fi. For $50 not only do you get to nominate & vote in the final balloting, but you also get a digital copy of every nominated novel, novella, & short story!
This year I'm a supporting member of WorldCon for the first time, and I noticed that the Hugo's have a category for Best Fan Writer ("Any person whose writing has appeared in semiprozines or fanzines or in generally available electronic media during 2010."). I do believe Harry Potter and the Methods of Rationality counts, and I plan on nominating it. Even making it onto the ballot will probably expose it to a wider audience. Is anyone else here a WorldCon member and thinking of nominating MoR?