Do you want to use version control for IS fragements or just make a backup of a defined state? The approach would be different.
Version controle is quite rudimentary in IS 6.x and 7.x (introduced with 6.1), but you may look for WmVCs as posted before and perhaps WmSubversion (which is not supported and not yet very mature).
For backing up Packages there are several options.
Just make a backup of the filesystem (packages directory in IS dir)
For single packages use Packages - Publishing or even export from Developer
For a more sophisticated approach use Deployer. You can create a deployment project containing all packages, create new builds to have snapshots from different points in time and use Deployment maps to restore single packages from a build. The builds can be expoerted and versioned in filesystem or in a Version control system.
Personally I would recommend the approach using Deployer.