The Tornado History Project

April 1, 1974 Alabama Killer Tornadoes
"The Tornado History Project is a free, searchable database of all reported U.S. tornadoes from 1950-2009*. There are over 53,000 tornadoes currently in the database, each with its own map and forum. The project's main goal is to combine historical data with user submitted items (eyewitness memories, photos, videos, etc...) to recreate the history of as many tornadoes as possible."
The Tornado History Project, Blog