Interesting link to download Landsat images (MSS = Multispectral Scanner System, TM = Thematic Mapper and ETM = Enhanced Thematic Mapper). The images are not very recent but they are free. The resolution is of about 30m. Precaution : download only one image at a time.
Voici un lien intéressant pour récupérer des images Landsat (MSS, TM et ETM +) du monde entier et GRATUITES