Avira Secure Backup is a compact and easy-to-use online backup tool.
The program comes with 5GB of free storage space. That's not overly generous these days, but invite friends to sign up and you'll get an extra 500MB for each one, up to an extra 10GB.
The backup client itself is extremely simple. By default it'll back up your desktop, Documents, Music, Videos and Pictures folder, or you can specify particular folders to protect; settings allow you to configure your backup speed and the maximum size of files to be backed up, and that's about it.
There are at least plenty of clients, though, including for the PC, Mac, iPhone, iPad and Android. You can also access your data via a browser on any device. And there's an option to generate a link for any file or folder, making it straightforward to share data with others.
You'll have to get your data backed up first, of course, and that may take some time. We first set the program to upload at its maximum speed, and performance was horribly erratic, eventually stopping entirely. So we switched to automatic, and it then took more than 20 minutes to upload a 20MB file. (This was on a basic ADSL connection which we benchmarked as delivering only 0.38Mb/s upload speeds at the time, but that's still poor.)
Upload performance was poor in our first tests, but if that can be fixed then Avira Secure Backup will be a reasonable, if basic online backup service: plenty of clients, easy to use, and with up to 15GB of free storage available if you can get enough friends to sign up