Module to Create Historic Timeline Snapshots of Drupal Sites?
You should take a look at Aegir. Although it is more than a module, it has the functionality you describe. Basically what Aegir can do for you is create a complete copy (database, codebase and files) of your Drupal website. The catch here is that your Drupal site should be managed by Aegir as well.

On the more technical side, if you take a look at what Aegir does, you will notice that creating a copy of your website is performed by a number of drush scripts. These scripts could of course be used/modified to make your snapshots.