Resources:
History of Maps and Cartography

Coordinate Systems Overview
Datum Overview
Projections Overview
Google Maps GPS Visualizer
What is GPS? (Trimble's Website)
GPS Resource Page
Geocaching!!
What is WAAS?
Minnesota Department of Natural Resources Garmin GPS Extension Page
Penn State's Online GIS Postbaccalaureate Certificate

Penn State's Master's Degree Program Information
NPR GPS Article: GPS Goes Into the Wild
Geospatial Revolution Project
Modulation
How GPS Works YouTube Video Clip

Tools:
GNSS Mission Planning Online
PLSS in Google Earth (PLSGE)
Tools for Google Earth (Earth Point)
The National Map Viewer