You can use Google Maps and Google Earth to add your own data onto Google maps either by adding pins one at a time, or by importing data (with either longitude or latitude or place names) from a spreadsheet. You can also mark shapes on the map. Google Earth is slightly more complicated, but allows for 3D maps and the importation of historical maps (Rumsey Historical Maps are among the historical maps available). Your maps, like Google docs, can be easily shared for group work or public display, and embedded into other sites.
Examples:
Further Reading:
Intro to Google Maps and Google Earth