I am not an expert at evading tornado dangers, but I do know that, like many of you, I want to be. So I've compiled a list of resources to help us both achieve maximum tornado safety with the minimum amount of work.
You can boil down the Tornado/Storm Shelter into two basic groups: A) Your basic homemade installation and B) professional prefabricated units. The first may be cheaper and more attractive, but the second route is probably easier pending your cash situation.
It should be noted that I am not an expert. I cannot and do not vouch for the accuracy or safety of any of the options presented here. It's merely a list compiled to help you research the right solution for your specific needs.
A) Here are some hints, tips and plans to build your own shelter:OFFICIAL FEMA safe room construction plans from FEMA P-320, Taking Shelter from the Storm by FEMA.gov
How to build a tornado shelter by DoItYourself.com
How to build your own 10x6 storm shelter/safe room for under $2,000 by the SurvivalistBlog.net
How to build a low cost Earthbag tornado shelter by the NaturalBuildingBlog.com
B) Here are some sources of prefab units, most made in the USA:FamilySAFE Shelters
Purveyors of steel above and below ground tornado shelters.
SECUREALL Tornado and Hurricane Shelters
Suppliers of steel aboveground safe rooms.
Cozy Caverns Storm Shelters
Manufacturers of custom full steel below ground shelters.
The Refuge by Fiberglass Creations, Inc.
Manufacturers of fiberglass below ground shelters.
Tornado Master Severe Weather Shelters
Producers of above and below steel or concrete shelters.
Survive-a-Storm Storm Shelters and Tornado Shelters
Builders of steel above and below ground residential storm shelters, survival bunkers, community safe rooms and bulletproof panic rooms.
Flat Safe Tornado Shelters
Makers of flat lid, in floor shelters made from hot dip galvanized steel or Fiber Reinforced Plastic/Polymer.
Verdict: Heads down and spirits up. Good luck out there, people.
Image: US Air Guard responds to Moore, Ok Tornado via US Air Force Material Command.