FONBackup is a freeware that lets you sync any folder on your computer to Gmail. It makes use of free space available on Gmail, and stores your backup in that. You can even configure multiple Gmail addresses in this, and then backup multiple folders on your computer to those Gmail accounts.
FONBackup is quite simple to use. Download and install the software (by double clicking on downloaded JAR file). Then configure your Gmail addresses in this program. You do not need to use your regular Gmail account with this; you can create new Gmail accounts for backup purpose.
After that, just pick the Gmail account to which you want to backup, and pick local folder of your computer that should be backed up. You can backup only one folder to one Gmail account. To backup multiple folders, you’ll need to create multiple Gmail accounts.
If you are using Gspace, this integrates with that too (it actually comes from the same company). So, the folder that you sync through FONBackup can be integrated using GSpace Firefox extension also.
FONBackup is completely free. As I mentioned in the article about GSpace, I would always be scared that Google might block these type of services any time. So, I would use FONBackup to sync non-important folders, like, music folders. And use more reliable services like Dropbox alternatives or Mozy Alternatives to backup important documents (even DocStoc would be a good choice).
Download FONBackup free.