This application converts your android device into an FTP server. You can download/upload, and modify your files from your computer using any popular FTP client, like FileZilla.
NOTE: If FTP URL is in RED color, it means you are connected with mobile packet data. Using it with mobile packet data may cost money. It is advisable to use this application with Wi-Fi connection.
This application could be useful for devices not supporting USB Mass Storage option, as well.