I’d suggest the Red Cross / Crescent
http://www.asiaearthquake.redcross.org.uk/tsappeal/appeal.asp

they work with volunteers at the frontline, deploy professionals (doctors, comms specialists) as appropriate and have the clout needed to get past the politics and bureaucracy which can get in the way of aid efforts. they are also not linked to any one nation and have been proven as neutral in wartime.

Incidentally if I supported a charity I’d like to support one which works both overseas and in the UK; whilst its on a far smaller scale there has also been serious damage in Britain from extreme weather conditions (Cumbria/Scotland in particular) and people here will also need help – the Red Cross also does this!