The ascent of Mt Audubon from the Mitchell Lake TH is 3.9 miles with 2700 feet of elevation gain.  This is a VERY popular hike.  Note that you need a reservation to enter the Brainard Lake area of the Indian Peaks by motor vehicle during the peak season (mid-June through mid-October).

The Ascent and Round Trip have Strava segments.

Dave Shumway posted the route:

The Beaten Path travels 26.6 miles from East Rosebud to Cooke City.
The Ultra Beaten starts at East Rosebud, runs to Clarks Fork Trailhead (near Cooke City), and then back to East Rosebud, turning a common 3-5 day one way backpacking trip into The Ultra Beaten (53 miles - 85 kilometers).

http://www.simblissity.net/get-home.shtml

The G.E.T. offers a wild, scenic, diverse, yet also convenient way of discovering some of the most fascinating and little-known corners of the American Southwest.

Lawton Grinter posted the route: