I've been lurking here for six months or so; I think I got here from Overcoming Bias through a link from Marginal Revolution. I try not to come here more than once a week because I end up spending too much time here due to the extensive interlinking.
Some research says that lurkers make up over 90% of online groups. I suspect that Less Wrong has an even higher percentage of lurkers than other online communities.
Please post a comment in this thread saying "Hi." You can say more if you want, but just posting "Hi" is good for a guaranteed free point of karma.
Also see the introduction thread.