alt.polyamory FAQ, The best place to start if you're curious. It's also found below.
Loving More Magazine - New Models for Relationships
The Polyamory Index
A couple of other Alternative Lifestyle Sites
Communities (communes, co-husings, co-ops, ...)
Network for a New Culture, the American offshoot of ZEGG, The Center For Experimental Cultural Design, a German group that has been working since 1978 to design a way of living together without hate and fear.
My being polyamorous doesn't mean I want to have illicit sex with a woman who is the (ostensably) monogamous partner (wife, girlfriend, etc) of someone else. I think that people should keep the agreements they make, and I don't want to participate in a woman's violation of an ongoing agreement she has to be fidelitous to another person. If I didn't believe in that strongly, I wouldn't have considered and rejected the notion of making such an agreement myself. Almost all of the poly people I've encountered feel this same way.