you could also try BackupLoupe. I use both this and TimeTracker. TimeTracker will (mostly) automatically mount the Time Machine drive and image (if on a remote/network drive), while with BackupLoupe you need to mount the drive first.
BackupLoupe also has a great interface for finding files backed up, as well as giving a colour-coded view of the size of backups and, as you dig down, folder by folder. It also has a much better interface for excluding files from a backup (the Apple System Preferences for TM only show up if the file / folder currently exists, but BackupLoupe will always show them.
Also, FYI, Time Machine automatically excludes certain folders, and this includes all caches that are located in standard locations, as well as temporary files.
(Note: If you are using a network drive, such as an airport disk or Time Capsule, I have noticed that with 10.6.4, manually mounting the image with Finder (which you have to do with BackupLoupe), is causing performance issues. I therefore recommend using TimeTracker to mount the image automatically, and then run BackupLoupe).
For anyone that wants to know what is being backed up and when, BackupLoupe is brilliant. It's only $5, and even then it is an honour system, so you don't need to pay if you don't really use it or like it.