I've been a member of the Naturephotographers.net (www.naturephotographers.net) for some years now - and recently joining the regional Colorado Nature photographers group. This is a group of serious amateur and professional nature photographers - most living along the Front Range area. They get together for improptue photo outings all year long. If you'd like to join a group of friendly like-minded folks, I'd encourage you to check out their forum section. If you join, you are also given an area to post your portfolio. They may be found at http://colorado.naturephotographers.net/index.shtml.
Their annual get together is happening Jan. 28th at 5:30 pm up in Denver. Check out the details on the forums section!