Fraser/Winter Park, CO in August

There's rafting and zip lining along Clear Creek, which I-70 follows along from the tunnel down to the Hwy6/Golden/Clear Creek Canyon exit.

Clear Creek Rafting

Liquid Descent

Both are based in/around Idaho Springs along i70

Zipline

LINK

I've you've never ziplined before, I guess you have to try it once to see what it's like. This one is pretty lame relative to other zip lines. I see it as one of those things you do once to experience it, but ziplining isn't something cool enough to go do again. Unless you go to a badarse zipline course that has long lines over super deep canyons, but most of those are in Central/South America and New Zealand.