Geographic Information Systems (GIS) utilize a variety of technologies to gather and manage information about the world. It has many applications in Science, Social Studies and other disciplines. Global Positioning System (GPS) utilizes satellites to determine location, velocity etc.

"A GIS gives you tools to answer questions about a location (geographic information). You can combine layers of information stored in a database that may include addresses, aerial photographs, satellite images, dates, and other numerical values."
"A GIS does more than tell you "where," but can also answer questions like "why" and "what if?" With a GIS, you can explore relationships, trends, and conduct analyses that can be represented as maps."

http://edcommunity.esri.com/

You can download free software here. http://edcommunity.esri.com/software/index.cfm

"GIS allows us to view, understand, question, interpret, and visualize data in many ways that reveal relationships, patterns, and trends in the form of maps, globes, reports, and charts. A GIS helps you answer questions and solve problems by looking at your data in a way that is quickly understood and easily shared."

http://www.gis.com/

Here are some other sites that may be interesting.

http://www.gisetc.com/
http://serc.carleton.edu/sp/library/google_earth/index.html
http://www.isat.jmu.edu/stem/index.html
http://ict-in-science-education.wikispaces.com/GIS.GPS+Virtual+Field+Trips

Create a free login account to access GIS & GPS lessons here. Look for Free Educational Resources. http://science-approach.com/

Trimble GPS tutorial