Interactive Map software or web 2.0 tool?

I am looking for suggestions for creating interactive maps in the 9-12 grade history classroom.  I've worked with google maps and google earth a bit, but wondered if there were any other suggestions on great tools students can use to generate interactive maps.  I'm looking for something where they can create tours and visual representations of concepts like westward expansion, movement of peoples/cultures, etc. (think big arrows, segments with different colors, etc).  I look forward to your recommendations.  - Jeremy