To find the files that may be too large, or unnecessarily backed up, I use Disk Inventory X, an application that scans your current hard drive contents and gives you a visual representation of the files on your HD as well as the space they are taking up. (I've used with Leopard and Snow Leopard)
Once you identify any files as ones you don't want a bunch of back-ups of:
- connect your time machine backup drive
- click on the time machine logo in the menu bar
- select "Enter Time Machine"
- navigate to and select those files/folders in the Time Machine window
- click on the gear menu icon
- select "Delete all backups of
Time Machine will prompt for your password and delete all of the backups of the file/folder. You can then exclude these files/folders from future backups. To do so:
- go to the Time Machine preference pane in the System Preferences
- click "Options..."
- add the file/folder you wish to exclude from future backups
Note: Files such as sleepimage are system files, and removing from backup could cause unexpected behavior if you ever need to restore your system from a Time Machine Backup. sleepimage is a file that is the size of the amount of memory in your computer. Actually, I'm not even sure that Time Machine backs up this file. The moral: dont delete system files from your Time MAchine backup, use this method only for your personal files such as your iTunes Media folder or your iPhoto Library. Also, files which I exclude from backups I make sure to keep my own personal backup on a different hard drive.