Aspen is tucked deep in the Colorado Rockies, so getting there takes some effort regardless of how you travel. The reward is the spectacular mountain scenery along the way.
The drive from Denver International Airport takes about four hours west on Interstate 70, then south on Highway 82. The route is beautiful but can have heavy traffic and icy conditions in winter. In summer, Independence Pass offers a paved shortcut, though it is steep, winding, and narrow -- not for the faint-hearted or the impatient.
There are regular 40-minute flights to Aspen-Pitkin County Airport from Denver. Winter weather frequently causes delays, so build some flexibility into your schedule if flying in during ski season.