is a company formed by French Space Agency CNES and is one of the first commercial company to distribute satellite
images on a worldwide basis. They can be found at http://www.spot.com/
You can find a Spot satellite image search engine on that website, called Sirius.
CRISP remote sensing centre in Singapore also provides a Spot satellite images search engine that is arguably better with more features and include satellite images product other than Spot. They can be found at http://www.crisp.nus.edu.sg/