I love this idea, and I'm in! I love the idea of doing the American Discovery Trail, too -- everyone can stop by my house for a virtual McDougall lunch in Maryland!
I think Letha is right that we should do it like the MWL thread, which has been so successful -- one big group, with people reporting their mileage once a week. And counting minutes of exercise as miles is a great idea too. That's basically how the Leslie Sansone DVDs work. Depending on how strenuous the workout is, on her DVDs a mile takes anywhere from 12 to 15 minutes. It sounds like the group is leaning toward saying 10 minutes=1 mile, which is fine too (I tend to think in terms of 15 minutes being a mile, because it takes me at least that long to walk an actual mile outside). We should do whatever will encourage the largest possible number of people to participate.