A number of established charities from UNICEF to Save the Children are soliciting financial donations to assist in the relief effort. In the early stages of disaster relief, it's better to donate cash rather than supplies as organizations on the ground can route money exactly where it's needed. Material donations like food, clothing and supplies tend to require transportation, which is expensive and currently presents logistical challenges with many roads destroyed or flooded.
When donating funds, it's best to go directly to the charity's website and set up a payment from there. Some organizations may have plans to focus on different aspects of relief, so do a little research to determine exactly where your money is going.