I think something that may help you to understand polyamory is the book "The Ethical Slut" by Easton & Lizst. In it, it does a good job of describing the feelings and the relationships of ANY type of non-monogamy. Personally, we love the phrase "ethical non-monogamy" because it fits!
Polyamory isn't just about deep romantic love of more than one, but it is about more than just fun sex. Don't get me wrong, I am sure somewhere out there is someone who can and does love more than one person at the incredibly deep and sensual level. But think of your own life now. You love your family, your children, your close friends - but all differently. There are so many different levels of love. THAT is polyamory. Much of it is really deep intimate friendships that cross into love and sexuality (so I always ask, if that is true then aren't we all poly?
). It's a very gray area, and not at all a singular definition although there are "factions", like the three-way "marriage" described above. The most open minded folk believe that the close friendships and repeated meetings between swing couples is a form of polyamory. You know, that one couple you can hang out with, travel with, do regular things all afternoon on a Saturday...then come back home and everyone piles into bed and the fun begins? That, my friends, is a form of polyamory. Poly relationships come in many forms and there is no "standard" but triads are by far the most well known.
Anyway, just wanted to add a little more to the discussion. "Love Without Limits" by Deborah Anapol is also a good reference. And besides
www.lovemore.com, there is also
www.polyamory.com (usenet) as a resource.
Forgot to add that the "commitment" between parties may vary, and often Poly relationships are very open as long as some type of "Condom Commitment" is honored. Poly also means more partners to protect and consult re: sexual activity! Like swinging, "cheaters" ain't poly!!