From 4LPH41337.com

Mapping

• UTM interaction tool for Google Maps
• Google Earth USGS Topo Maps
• How to output Google Maps to KML and other URL manipulations
• Google KML file to GPX converter app
• GPS File Converter and Elevation Lookup -- Pretty powerful!
  • Can plot a map or profile based on a gpx/kmz/csv file
  • Can convert between almost any format
  • Generate Elevation Profiles from Google Map Directions or gpx file with elevation data: Use GPS Visualizer
• Garmin's Activity Tracker
• Trail Locator
• Topographical Maps

Paddling

• National River Database

Other

• Hydration Requirements Calculator
• Weather