Pack Your Bag:
Every year Sierra Club
volunteers donate 25,000 hours to help preserve hiking trails for future travelers. Projects range from rooting out invasive plants in California's Yosemite Valley to rebuilding trails in Kentucky's Mammoth Cave. Family programs mean preservationists as young as 5 can get their hands dirty for a greater cause.
typically one week
$315 to $1,975, including meals and lodging
Quick Trip: The Appalachian Mountain Club
and the Tahoe Rim Trail Association
offer weekend trail repair projects.