Heading up the mountain on skis has gained popularity around the nation. Most resort have designated trails, access times and a set of rules (check website) – but it's free to travel uphill.
Free uphilling at Buttermilk. (Aspen-Snowmass)
Scheduled to shut down its lifts on April 2, operators of Buttermilk Mountain have decided to open back up on April 8-9 for all manner of human-powered uphill traffic.