Backpacking

All Trails (Hiking Trails)
Appalachian Mountain Club
Hiking in Colorado
Red River Gorge Geological Area
Pacific Crest Trail Association
Trailsource (Hiking Trails)
Adirondack Mountain Club
ALDHA: Appalachian Long Distance Hikers Association
American Hiking Society
Buckeye Trail
Washington Trails Association

Caving

National Speleological Society
American Caving Accidents
Dayton Underground Grotto
Greater Cincinnati Grotto
Great Saltpeter Cave Preserve
Carlsbad Caverns National Park
Jewel Cave National Monument
Mammoth Cave National Park
Oregon Caves National Monument
Wind Cave National Park

Mountaineering
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Summit Post
Alpine Ascents International (Guide Service)
The American Alpine Club
American Mountain Guides Association
Colorado Mountain Club
14ers.com (List of all Colorado 14ers, routes and conditions)
The Explorers Club
The Mountaineers
Mountain Madness (Guide Service)
The Scottish Mountaineering Club
RMI- Rainier Mountaineering Inc. (Guide Service)
White Mountains Information Page

Rock Climbing

Mountain Project
The Access Fund
American Safe Climbing Association
Big Wall Climbing Home Page
Climbing Gym- Rock Quest- Cincinnati, Ohio
Climbing Gym- Urban Krag- Dayton, Ohio
The Red River Gorge Climbers' Coalition

Cycling

Adventure Cycling Association
League of American Bicyclists
Le Tour de France
Trailsource.com- Mountain Biking Trails
USA Cycling Online

Car Camping & Driving Info

Free Campsites.net (Free Camping across the US)
Kampgrounds of America Inc.  (KOA Official Website)
Google Maps  (Simply search Camping)
Weather Network Highway Weather (Weather Along Your Route)

Whitewater

D&D Outfitters (local retailer of canoe & whitewater gear)
Rafting Ohiopyle PA 
OA Guide to Planning a Safe River Trip
New River Gorge National River
Rio Grande Wild & Scenic River
River Gauges
Rivers Unlimited (Ohio)
USGS Real-Time Water Data
West Virginia Whitewater Resources

First Aid & Rescue

Wilderness First Aid Training  (Through NOLS)
Guide to Heat Related Illnesses & Fluid Balance
Guide to Hypothermia And Cold Weather Injuries
Wilderness Medical Associates Home Page

World Travel

U.S. State Department
CDC: Center For Disease Control / World Alerts
Currency Converter
Fodor's Travel Online
Lonely Planet Online
REI Adventures

Skiing (cross country & downhill)

Cross Country Ski Association
Intellicast: Ski Reports
North American Avalanche Information Centers
Ski Michigan.net
Trailsource.com- Cross Country Skiing Trails
10th Mountain Division Huts (Colorado)

Outdoor Education Resources

American Mountain Guides Association
Four Corners School of Outdoor Education
The Mountaineers
National Outdoor Leadership School (NOLS Outdoor Education)
Tom Brown's Tracker School
Voyageur Outward Bound
Outward Bound

Airline Reservations & Lodging

Google Flights (Air Travel)
eGO Travel Guides (UK Airport Information)
WOW air  (Trans-Atlantic Air Travel)
Ryanair (Discount International Travel)
Hostels.com (International Hostel Search Page)
Travelocity  (Airline, hotel and car reservations)
Directory of Country Inns and Small Hotels (Domestic Travel)

Weather

Mountain Forecast (Weather for 11,300+ Major Summits)
The Weather Channel - U.S. City Forecasts
Weather Underground- U.S. Forecasts
World Weather

Bookstores & Maps

Color Landform Atlas of the United States
TopoZone.com (Topographical Maps of the US)
Trails.com Maps
National Geographic USGS Maps
Wilderness Press Online

Local State Parks & Forests

Kentucky
Kentucky State Parks
Daniel Boone National Forest
Mammoth Cave National Park
Red River Gorge Geological Area
Cumberland Gap National Historical Monument

Ohio
Ohio State Parks
Ohio State Forests & Recreation
Wayne National Forest
Cuyahoga Valley National Park

Indiana
Indiana State Parks
Indiana Dunes National Larkshore
Hoosier National Forest

Government Resources

Bureau of Land Management
Library of Congress
The National Park Service
U.S. Forest Service
U.S. Environmental Protection Agency
U.S. Fish & Wildlife Service
U.S. Geological Survey
U.S. Naval Observatory (sunrise/sunset, moonrise/moonset)

Environmental & Conservation Groups

Leave No Trace Outdoor Ethics
National Parks and Conservation Association
The National Speleological Society
Sierra Club
Southern Utah Wilderness Alliance
Wilderness Society Home Page
American Whitewater Affiliation
EnviroLink: Online Environmental Community
Environmental Organization WebDirectory!

Odds & Ends

Cincinnati Astronomical Society
ORRRC (Ohio River Road Runners Club)
The Mountain Zone (Outdoor activities, expeditions, travel, etc)

Equipment & Suppliers

Roads Rivers and Trails (Located in Milford, Ohio)
Benchmark Outfitters (Located in Norwood, Ohio)
REI: Recreational Equipment Inc (Location in Norwood, Ohio)
Sierra Trading Post (Location in Columbus, Ohio)
Backcountry.com (Online retailer)
Karst Sports (Caving Gear)
Rainy Pass Repair, Inc. (Repair Service)
On Rope 1, Inc. (SRT equipment)
Specialized (Bicycling gear)

National Parks, Forests & Recreation Areas

USDA Forest Service
Acadia National Park
Arches National Park
Badlands National Park
Bandelier National Monument
Big Bend National Park
Big South Fork Recreation Area
Bridger-Teton National Forest
Bryce Canyon National Park
Canyon De Chelly National Monument
Canyonlands National Park
Capitol Reef National Park
Chaco Culture National Historical Park
Colorado National Monument
Crater Lake National Park
Death Valley National Monument
Devils Tower National Monument
Dinosaur National Monument
Everglades National Park
Gates of the Arctic National Park & Preserve
Glacier National Park
Glacier Bay National Park & Preserve
Glen Cayon National Recreation Area
Grand Canyon National Park
Grand Staircase-Escalante National Monument (BLM)
Grand Teton National Park
Great Sand Dunes National Monument & Preserve
Great Smoky Mountains National Park
Guadalupe Mountains National Park
Hovenweep National Monument
Isle Royale National Park
Lake Chelan National Recreation Area
Mesa Verde National Park
Mount Rainier National Park
Natural Bridges National Monument
North Cascades National Park
Olympic National Forest - Olympic Peninsula Washington
Olympic National Park
Organ Pipe Cactus National Monument
Pictured Rocks National Lakeshore
Point Reyes National Seashore
Rainbow Bridge National Monument
Redwood National & State Parks
Rocky Mountain National Park
Saguaro National Park
Shenandoah National Park
Sleeping Bear Dunes National Lakeshore
Sunset Crater Volcanic National Monument
White Sands National Monument
Yellowstone National Park
Zion National Park