We have a thread somewhere 'round here about online dating sites where poly folk can be found. I don't remember where it is, right off hand, though somebody can probably point it out for you. Or you can use the search feature.
When speaking of various forms of non-monogamy...it ain't poly if you're just fucking around.
While polyamory, open relationships, and swinging are all distinctly different approaches to non-monogamy, they are not mutually exlusive. Folks can, and some do, engage in more than one of them at a time--and it's all good.