If you go on Denver's Momslikeme.com site, there are lots of natural parenting forums there. Also, there are a few on CafeMom for natural parents in Denver.
If you look on Meetup.com, you will find a few there too, my favorite being the Holistic Moms Network. Our HMN chapter here in Denver is pretty awesome. There also used to be a group called something like Golden Natural Mamas and Papas, but I'm not sure if that group disbanded or not. Broomfield isn't TOO far from Golden, but it still might not be worth the drive for you. You might check out the Denver Metro Urban Homesteaders group too, there's a lot of natural parents there. Where are you moving from?