If you’re flying, the Denver International Airport is convenient to Boulder, about 50 minutes away from the seminar location. United Airlines has a hub there, so that’s often a good choice. Frontier and Southwest also have hubs in Denver, and are typically less expensive. (Airlines have a much larger number of nonstop flights to their hub cities).
Information about traveling to Boulder is available on the Boulder travel guide on WikiTravel. It includes information about shuttle buses, restaurants, and lodging, as well as recreational activities. It also includes budget hotels, hostels, and B&B’s (and there’s also Air B&B).
Alternative Lodging: If you’re up for camping, Boulder boasts some nearby campgrounds. While we have no personal experience with the campgrounds, you might check out Boulder Campgrounds.