Google Earth is the most fantastic digital geography resource yet devised. Try it today - assuming you have a fast, modern PC and a rapid internet connection.
Download the program here
Once you have it installed and have mastered the controls, you'll soon want to add some of the thousands of great OVERLAYS and extra DESTINATIONS which people have posted on the web.
Try the Google Earth Community for starters.
Just as good is Google Earth Hacks
A very few cool ones to get you started (opt to "Open withGoogle Earth" when downloading):