The tsunamis have come and gone, but in the aftermath there is now a massive medical crisis around the Indian Ocean. Children, disproportionately affected by the initial disaster, will also be more vulnerable to the host of diseases that inevitably follow something like this.
Direct Relief is based in Santa Barbara, and provides primarily medicines and other supplies to disaster-stricken areas.
While the international relief effort is gearing up, Doctors Without Borders already has put teams on the ground and is flying in more doctors and other medical specialists tomorrow.
More information on the situation and charities that are helping is here.
I strongly recommend you check out any organization you're planning to give to using Charity Navigator.
Also this blog, which is run out of Asia, is a good portal for up-to-date information about the crisis.