Mainly for my Belgian readers: I recommend having a look at Oxfam Solidarity, specifically their special South-East Asian tsunami fund. Because of the ludicrous Belgian tax system, every euro you give to charity here is multiplied up five or six times in its effect as long as you do the paperwork right.
I’m particularly keen on Oxfam because I see them combining the on-the-ground humanitarian stuff with political analysis. It may be an unfair impression, but I seem to see more of them doing the necessary politics in Brussels than any of the others. While some people complain when a charity does politics as well as good works, I think the former is an essential part of the latter.