FileRunner is a two pane file manager for Unix and Unix like systems. It is simple and efficient and has a built-in FTP and SFTP client. It also does a reasonable (and improving) job on Windows systems. New and improved from a FileRunner of long ago.
ChemVisio is software which might be useful for educational purposes (non-organic chemistry, crystallography etc.). It might be a good visualization support for all people who need better illustrations than that you could see in books.