http://www.savethechildren.org/

You can specify which country you want to send your funds to, including for children of the US. Right now they are trying to aid children in South Asia following the flooding brought on by monsoons. They also have a matching gifts campaign. This is the orginization American Idol, AT&T, Ford and others raised funds for last spring. On AI, they showed in Africa how $10 would buy a mosquito netting to protect a family from malaria, and $6 would pay for malaria vaccine that could save the lives of 4 children. Incredible work.

Doctors Without Borders is also great.

Always the local no-kill animal shelter/Humane Society.