The Millenium Hotel is located at 1345 28th St, Boulder, CO 80302.  The closest airport is Denver International. 

The SSE has negotiated a discounted shuttle service from Denver International Airport to the Millenium Hotel through Green Ride Boulder.  It is $29 one way.

For the budget-minded, Google Transits lists several options by bus and rail.  Note, however, that all routes require at least one change of line and at least part of the journey is by bus.