Here is the donation form for red-cross.
http://www.redcross.org.hk/donation/SouthEastAsia041227/donation%20form-Bay%20of%20Bengal%20quake%20n%20tsunamis-1.htm
You can use various payment method including credit card for the donation. Just fill it in and fax back to the red cross office. Donation over $100 are eligable for tax deduction.