Google Earth renders a 3D representation of Earth based primarily on satellite imagery. 

How It Can Be Used:  Google Earth can be used for many different subjects. Think about taking your history class to historical sites, or taking your science class to the Grand Canyon, or taking your English class to England  for a topic in your British literature class.

Google Earth can also be used:

• to support hands-on inquiry by students in computer classrooms.

• for dynamic presentations during class lectures and inquiry during presentations

• to create imagery and maps for PowerPoint, Word, and other presentation tools.

• as a data discovery, organization, and distribution tool for research projects.

• to enrich discussion of an issue that arises spontaneously during an informal classroom discussion.

(Source:  How to Use Google Earth in the Classroom)

COST:  Google Earth is free for faculty, staff, AND students.