The current generation of satellite air quality instruments are able to provide high-quality information on pollutants such as NO2, SO2, CO, particulate matter, and others in the boundary layer. However, a proper interpretation of these measurements requires the use of additional information supplied by sophisticated atmospheric models. A description of current algorithms and their limitations will be presented along with a summary of available data products and their applications. Specific results of pollutant mapping from satellite over diverse natural and anthropogenic sources will also be shown, including volcanoes, urban areas, power plants, and the Alberta oil sands. A new satellite-based method to estimate the emission strength of NOx and SO2 from isolated point sources will be introduced.