You can customize what Time Machine does not back up by using the following plist:
/System/Library/CoreServices/backupd.bundle/Contents/Resources/StdExclusions.plist
Simply add the strings that you don’t want to back up and it will no longer back up those locations. Remove the strings to re-add them at a later date.
In the UserPathsExcluded key, you can exclude paths that in relation to users home directories.
