The guide linked to the right is the best place to get a sense of all the options available to you for finding economic statistics. If it would help to have a shorter list of places to start, try the following:
Relative levels of income, output, inputs and productivity, covering 167 countries between 1950 and 2011. TIP: Scroll down to the "online access tool" to select the measures, countries, and time period you want.
(Searches through citation information)
Thousands of time series covering more than 200 countries and areas, published by the IMF (International Monetary Fund). Covers 1945 - current.
National Statistical Agencies
Search for the country name and 'statistics.' Most countries have a national statistical office (the US excluded), which will provide access to frequently used statistics.
Macroeconomic Statistics
The ECON 110 Guide to Macroeconomic Statistics provides an overview of major sources of statistical data about the health of economies. Explore the sources on the guide and do not hesitate to contact me for help.