The Colorado Department of Transportation today announced that Guanella Pass is open for the season, weather permitting. Independence Pass opened earlier this week.
The opening of Guanella Pass, which connects I-70 to U.S. 285, also opens up access to high-mountain trailheads including the Mt. Bierstadt trailhead. (You still might want to wait a little for that hike, though.)
Independence Pass, or Colorado 82, will get you from Twin Lakes to Aspen and, of course, there's plenty of good hiking to be done up there, too.