Our family donates to the Red Cross, Descartes having seen them in action when he lost his family home in the Berkeley/Oakland Hills fire.
They have made it very simple to donate. Simply text Haiti to 90999 to donate $10.00 to Red Cross efforts. It will be billed to your mobile phone bill.
I also received the following list of charities from Lucy's school. It was compiled by the National Association of Independent Schools.