Don't let your worries about scams stop or slow your donations. You can certainly start here: The American Red Cross. Or the equivalent outside the United States. Or take your prayers and a check to your own house of worship. We should be getting good at this, especially after the Tsunami in SouthEast Asia.
You can take a chance and throw a few bucks at a collection can, if you don't recognize the agency collecting, but I'm willing to bet that they'd be content to hear that you've donated through one of the reputable, widely-recognized national and international agencies.
Update: It is very difficult (tedious) to give online right now. Try your local chapters.