This humanitarian organization, a co-recipient of the 1997 Nobel Peace Prize, focuses on relief efforts and has worked in nearly 90 countries. They have been on the ground since day one and report that 100% of donations will go directly to tsunami relief efforts. You also may donate United miles.
Phuket Tsunami Recovery Fund
This fund was organized by James Batt, Joint Managing Director, on behalf of Laguna Resorts & Hotels. The hotel company is covering 100% of administrative costs, so that every penny of donations goes to relief efforts.
Habitat for Humanity
Already very active in this part of the world, Habitat has plans to build 25,000 homes for displaced tsunami victims. You can designate your donation for their Asia Tsunami Response Fund.
The HQ site has compelling reports on conditions and relief efforts, as well as a place to donate. There also is a USA site.
Christian Children's Fund
You can support CC's relief efforts aiding children in India, Indonesia and Sri Lanka through its special ChildAlert Emergency Fund.