I definitely want to second the use of OKCupid. If you're feeling nervous or hesitant, you can just put up a profile stating exactly what you want out of the site: dating, relationships, good friends, etc., and then you sift through the responses. My experience with it is limited, since we've basically only used it to search for casual sex partners at this point, but there's definitely a fairly strong poly presence on it as well. The real good thing about it is, unlike most dating sites, it's free. So you can sign up casually and don't have to feel pressured into using it immediately.
(And no, I'm not on OKC's payroll. : P I've just had a lot of good experiences with it.)