Dropbox - Online Sync and File Sharing
MailStore - MailStore Home - A 100% free single-private-user desktop solution
Box - Box offers secure content management and collaboration for individuals, teams and businesses, enabling secure file sharing and access to your files online.
Gmvault - Backup the emails in your Gmail account.
Google Drive - Access and sync your files anywhere
Got Your Back - Got Your Back (GYB) is a command line tool that backs up and restores your Gmail account.