BackupLoupe is an alternative GUI for Time Machine. At its core it provides a Finder-like interface where you get to select a snapshot and it will show you what has been backed up.
BackupLoupe shows you which files take up the most space in an instant. Scanned snapshots are color-coded so you can tell the big ones from the small. Select a snapshot and the browser view will list all items that have been backed up ordered by size in descending order.