VirtualFolders 0.1.1a
From the documentation:
Edit: For information on how to use this for VM snapshots, see this how-to.
From the documentation:
What is VirtualFolders?
VirtualFolders is a program designed to allow its user more flexibility in filesystem management. Not only does this program allow for undoable folders that only store modifications made to them, but it also allows editing of filesystems stored on some read-only media. There are many possible applications,but here are some examples:
-Virtual machine snapshots
-Keeping backups of an original when making modifications to a project without having to use the disk space required for a copy
-Mounting a backup on CD or DVD as read/write
Edit: For information on how to use this for VM snapshots, see this how-to.