Interactive explorations of history
The University of Oregon's Mapping History site could easily suck up all your productivity for a day or two
. Filled with interactive graphs, charts, and timelines, it allows you to explore history in the United States, Europe, Latin America, and Africa. The US section is particularly robust, allowing you to trace everything from the development of railroads, to connections between the growth of the cotton and slavery industries, to changes in life expectancy. Fascinating and fantastic.