Windows: Backup utilities that save your user profiles (including documents and application data) usually only do so from one user account at a time. If you want to back up multiple user profiles without having to log into each account, check out DataGrab.
The free DataGrab utility lets you select the folders within each user profile you wish to back up, including Documents, favourites, and application history. You can also select specific file types to save, such as Word docs or wildcard extensions of your choosing.
Once you've selected your backup options, you can save the backed up profile (a DataRestore.exe executable file) to either a local or external drive location. In my tests, the backup was pretty fast, but did present several Windows prompts about folder lengths and copy confirmations (something that may have been avoided, per AddictiveTips by choosing the "Use Unstoppable Copier" option under the Copy Method menu). When the backup is complete, you'd only need to run the executable to restore all the user profiles.
The utility can run from a portable environment (e.g. USB flash drive), though there's no built-in scheduler currently for the backups.