GoodSync - GoodSync provides highly reliable file backup and synchronization for both individuals and businesses.
WebDrive - WebDrive File Access Client allows you to open and edit server-based files without the additional step of downloading the file.
rsync - rsync is a file transfer program for Unix systems. rsync uses the "rsync algorithm" which provides a very fast method for bringing remote files into sync.
ifttt - IFTTT puts the internet to work for you. Create simple connections between the products you use every day.
Syncthing - Syncthing replaces proprietary sync and cloud services with something open, trustworthy and...
Air Explorer - Air Explorer is a software to manage all your multiple cloud drives (like Dropbox, Onedrive, Google Drive, Mega, Mediafire, Box, Hidrive, Yandex, Baidu,...) as well as WebDav and FTP connections.