There's never a good time to bring up this kind of subject especially after the recent devistation and loss of life from tornados. I recently saw a CNN segment on TV where a homeowner, who worked for an engineer, got plans from a fellow employee on what it would take to build a tornado shelter.
She used bi-directional, steel-reinforced poured concrete and built walk-in closet that doubles as a tornado shelter. What a great idea that's practical and worth the money invested to protect you and your family (and house pets) from the potential devestation of a tornado. Amazingly, this closet (er, tornado shelter), was completely in tact but the rest of the home was destroyed. As you would suspect, everyone in the shelter survived. :-)
I found FEMA's WEB page that gives a URL (link) to another FEMA WEB page where you can either download plans to build a shelter (for free) or send away by mail for the plans (for free). This is my good deed for the day. If anyone out there is at least thinking about building one, you can't go wrong in getting this info especially when it's free. I feel for everyone and their losses, people and homes. FEMA Tornado Shelter Brochure. Click on Taking Shelter from the Storm: Building a Safe Room Inside Your House to get to a page that gives the toll-free FEMA phone # and the outline on how to protect yourself from a tornado. There's a good picture on the 2nd page of this link: Tornado Shelter.