Via digg, from an article of the same title from BBCNews.com:

The Netherlands is the rich nation which does the most to improve lives in developing countries, a Center for Global Development (CGD) report says.

The UK is 12th in the annual Commitment to Development Index of the world's 21 richest nations and Japan ranked last...

The CGD's measures a broad number of factors for the index, rather than merely the amount of aid countries provide.

It also examines several policy areas - such as trade investment migration and environment - while aid is measured not only in terms of quantity but as a share of its income and the quality of aid given...

Meanwhile, despite the US giving the largest amount of aid that donation was the smallest in relation to the size of its economy.