No man is an island, not even Islandman from Marvel Comics*, and while I'm not entirely sure there's anything so coherent as an 'SF Fansite Community' out there, we here at Republibot like to occasionally point out other good SF websites.
Yeah, yeah, there's a kerjillion of 'em out there, but to have a truely good website on any subject there's kind of a balancing act between "I got me a computer and I know how to type, but don't have anything much to say" and the uber-commercial "We're only in it for the money because you geeks are suckers" sides of things. I like to think we're in the middle of that spectrum, but there's a whole lot of really good sites out there that perhaps aren't as high profile as they deserve to be.
One of these is "Big Dumb Object." Run by James Bloomer in England, it's a personal blog of SF-related topics. You've got your book reviews, overviews, opinions, episode reminiscences, and also a healthily-skewed viewpoint owing to the fact that it's *not* an American site, and Mr. Bloomer is an honest-to-gosh Scientest who's had an experiment performed at CERN. The site has been up and running since 2004, so there's plenty of stuff in the archives to wile away a day in an occasionally-thought-provoking way.
I'm particularly fond of his Apocalypse Watch section http://bigdumbobject.co.uk/apocalypse-watch/ but his "Cool" section is also a lot of fun http://bigdumbobject.co.uk/cool/ He's also a published writer, and some of his fiction is available online here http://www.bigdumbobject.co.uk/jamesbloomer/
Here's the main page. Check it out! http://bigdumbobject.co.uk/
*- I may or may not have made "Islandman" up. I've got a fever at the moment, and I'm hallucinating a bit, so I can't tell.