Company Backup Solutions

I am looking for a backup solution for our company. We would like to host it on our own server running Linux if possible. Windows is also an option.
I would need local and remote users to be able to backup their data. If it is automated that would be great but we could also look at an option where the user could login and copy data to the server. This needs to be as secure as possible and as user friendly as possible. I don't want to put anything in "shared folders". The kind of data we would backup would be documents, email, internet favorites and so on. I am really not sure where to begin looking for software and so on.
Thank you,