Seafile

Seafile

Seafile offers 100 GB Storage for $10/month but also gives you the opportunity to host on your own server. Your data is stored in Germany or with Amazon Web Service in the US for the cloud version. Encrypt files with your own password.

Client OS: Windows, Mac, Linux, iOS, Android. Server: Linux, Raspberry Pi, Windows.

Nextcloud

Nextcloud

Similar functionally to the widely used Dropbox, with the difference being that Nextcloud is free and open-source, and thereby allowing anyone to install and operate it without charge on a private server, with no limits on storage space or the number of connected clients.

Client OS: Windows, Mac, Linux, BSD, Unix, iOS, Android, Fire OS. Server: Linux.

Least Authority S4

S4

S4 (Simple Secure Storage Service) is Least Authority’s verifiably secure off-site backup system for individuals and businesses. 100% client-side encryption and open source transparency. $25/month for unlimited storage. Servers are hosted with Amazon S3 in the US.

OS: Linux, Windows, Mac, OpenSolaris, BSD. (Installation for advanced users)