I need to automatically fetch Landsat images and for that it would be handy to access a ftp with images available. Does such ftp exist? Can I access it? Ultimately I want to get cloudless images.
If you are not afraid of using Python for this you can use this little tool by CESBIO called Landsat Download. The only requirements are that you have an account on earthexplorer/glovis and the datasets you want to download are available online.
This will really depend on the archive times you are looking for. However, here is an FTP link to Landsat data. Most to all of the images are cloud free, or +/-10% covered: ftp://ftp.glcf.umd.edu/glcf/Landsat/WRS2/
Landsat 8 is now being digested by AWS. There is a standard directory structure and the data can be accessed via an http or through the AWS commandline interface. While this not an ftp interface, it will be quite easy to batch download in a scripting language.