Human Development Indicators

Human Development Indicators help measure "a new way of measuring development by combining indicators of life expectancy, educational attainment and income into a composite human development index, the HDI. The breakthrough for the HDI was the creation of a single statistic which was to serve as a frame of reference for both social and economic development. The HDI sets a minimum and a maximum for each dimension, called goalposts, and then shows where each country stands in relation to these goalposts, expressed as a value between 0 and 1."

The index has made it onto the free response question section of the AP US Government exam so this is a very important indicator.  The site has country profiles, rankings, data sets, GDP and more.