A "computational knowledge engine", Wolfram|Alpha is amazing in its abilities not only as a resource for historical and other information, but a useful tool for interpreting and using modern data. There are no links to other sites, results are from their immense collection.

Read the examples to get the most out of your searches.

Listen to a short speech from the inventor, Stephen Wolfram, presented at TEDTalks, labeled as "computing a theory of everything."