Got this data from NOAA via the spectacular Data.gov. It tracks 56 years of tornado paths along with a host of attribute information. Here, the tracks are categorized by their F-Scale (which isn't the latest and greatest means but good enough for a hack like me), where brighter strokes represent more violent storms.
Animations and Stuff
Check out the interactive version here.
Check this tornado tracks map broken out by F-Scale here.
Check this tornado tracks map broken out by seasonality here.
Check this tornado tracks as a print, available here.
Animated by month or by year.
Here is a more recent breakout of tornadoes by the direction they traveled.
Here is an updated version of the Tornado Tracks map with newer data, including the horrible 2011 season. Thanks to NOAA's http://www.spc.noaa.gov/wcm/ for the historical csv coordinate dataset and Adam Hill for development. Interestingly ('excitedly' if you are a supernerd), while the original was a manual creation, this update is based on a raw export from Visual Fusion. Export your own from the interactive version, here.
Click image for waaay higher resolution options, or click here to make your own map in the interactive version.
Other Sort-Of Related Maps
If this map is interesting to you, you might be amenable to plunging down the rabbit hole of related visualizations...