In UK? - Help Through Disasters Emergency Committee

The Disasters Emergency Committee of Great Britain co-ordinates the fund-raising of a number of UK charities (Oxfam, World Visions, Save the Children, Merlin, Help the Aged, Concern, Christian Aid, Care, Cafod, British Red Cross and Action Aid) in cases of extreme emergencies, which require more help than any one charity can provide alone.

They are currently co-ordinating fundraising for the Tsunami earthquake.

You can donate on-line, but their webserve is very busy, so you may find it more easy to donate via their phone line: 0870 60 60 900