Interested to improve your history for free? Try this... Go to MIT's OpenCourseWare website and browse to the history section. Download any coursework file and have a look at the essays that the students are suppose to write on.
Do your own research (reading) at wikipedia and read up on the articles.
Good if you have some time to spare. Hey... even though I posted this during office hours, doesn't mean that I waste company time to do this. But that's a thought.