World Development Indicators Online
Contains statistical data for over 800 development indicators and time series data from 1960, for over 200 countries and 18 country groups. Data include social, economic, financial, natural resources, and environmental indicators. Offers many useful features: results can be scaled, mapped, and charted; the mapping function allows users to see the results in a world map that can be resized and zoomed to the country level; data can be exported in standard formats such as Excel.
The Development Data Group of the World Bank. Information about their methods of data collection can be found here.
1960 to present