There are a number of organizations, such as the Organization for Economic Co-operation and Development and the International Monetary Fund, that study and present information about global and national economic growth to the general public. These organizations also have more detailed information on economic indicators related to overall national growth.
Both the OECD and the IMF have websites with many articles, charts, maps, statistics and projections concerning the economic outlook of countries around the world. One important statistic in particular is GDP, or gross domestic product. The OECD has a map showing scales of growth around the world based on each country's GDP. This map is missing data on quite a few countries, however, as of 2015.
The IMF has a more thorough growth data section by country that is more complete. In addition, there is a lot of information about the different sectors of an economy, such as real, fiscal and financial, as well as information about consumer prices, liquidity, stability and other economic indicators. The IMF website has a list of all countries with relevant economic research listed by country. This information is much more technical than the simple growth rates described by the maps provided by both the IMF and the OECD.
One final resource is the Economist magazine, which is a well-known and trusted source on economics. It has a list of countries and a description of each one's economic growth, including GDP growth, GDP per head, population and inflation, which is all available on their website. However, it is only possible to see a few articles without a subscription. In contrast, the OECD and IMF both offer free information about economic development.