Beyond the site itself, which I think will become an oft-used resource for me, I also really like their badge system. I think a similar system could be a huge boon to any forum, social networking site, or other community site. Game developers learned years ago that people will be more active in an area they already enjoy if they can be recognized for their activity. The same idea applies just as well to community sites. I think it's brilliant, and I think we're going to be seeing similar implementations a lot more often.