Mile Hi Con
is the major Denver SF con - 44 years and counting. This year's GoH is Cherie Priest, so I suspect there will be a strong Steampunk flavor this year (though last year had plenty of steamy programming, too!).
I was remembering that the Mile Hi Con organizers were heavily involved in the WorldCon production in 2008, but I'm unable to verify that independently.
BB Blackdog - it was a definite pleasure chatting with you at AnomalyCon this year. Would welcome you back to Colorado anytime!