If you have loved ones in Oklahoma, try texting rather than calling. Also use the Red Cross Safe and Well site to search for family and friends who've listed themselves safe.
Another important tool for everyone to use is the Red Cross tornado app for iPhone and DROID users. The app features tips on how to be prepared before, during and after disasters, NWS maps and information, shelter locations, and an "I'm safe" button to be used through social media accounts. The app also includes a built-in tornado siren that activates when NWS-issued alerts affect your area or the areas your friends and loved ones live in.