The GMU Library has plenty of links to geospatial data from USGS, Census, DOI and more.
Dimensions is a series of animated movies made by a group of mathematicians. The first chapter has a nice presentation of the geographic coordinate system and map projection.
National Geographic has tons of free maps and photos of our planet, and other planets too!
Google Earth is pretty much the best thing since sliced bread. You can also download Sketchup models of buildings and structures at the 3D Warehouse to achieve maximum fun. Yeah!
