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.
Hi.
edit: to add some potentially useful information, I think the biggest reason I haven't participated is that I feel uncomfortable with the existing ways of contributing (solely, as I understand it, top-level posts and comments on those posts). I know there has been discussion on LW before on potentially adding forums, chat, or other methods of conversing. Consider me a data point in favor of opening up more channels of communication. In my case I really think having a LW IRC would help.
http://webchat.freenode.net/?channels=lesswrong#
There it is.
(at least, that is how I know to access it...)