Thanks for the replies, especially you Nat. I knew you had some experience so I appreciate it.
ChupaCabra - actually, it's very likely we'll get engaged in the next 12 months. I actually don't feel the exact same way you do. Thinking of seeing my g/f and another woman go at it is certainly not unappealing to me, and afterwards, when she has a "girls night out" I won't be worrying. For one, none of her friends seems to share this interest, secondly, she refuses to be with one without me there, and lastly it's all about trust.
We've thoroughly discussed this, even more so in the past few days. She definately wants me involved, but says that I cannot have intercourse with or kiss this other woman. Anything else goes. That's OK by me since I'd never want her being nailed by some other dude, so I get where she's coming from. Not to mention this fantasy is hers, not mine...though I can't say I wouldn't enjoy being part of it.
Nat - thanks again for the advice. We've found a web site that's used for hooking up interested individuals and parties, so we've posted our profile and seeking out a 3rd person in our area. We don't want to "swing" with other couples, though the couples night and single womens night sound like possibilities. What is this Hedonism II? Sound like some sort of convention.