A graphical representation of the entire natural and human history. Use this app to build chart the timeline of your projects, whether it's history, geography, economics, art history etc.
There is a free version and paid version. The link above is to the free version.
The timelines are well populated (if not a little American Centric) with information, however the real beauty of this is that it is editable so students can build their own timelines, based on whatever topic you are teaching.