Recently I've been using ZFS for home backup, for the impressive data integrity and painless snapshot features it has built in. I've put together an OpenSolaris system and migrated my data to it, and came to the point of deciding how to manage snapshots.
Creating a snapshot with zfs is simple, but zfs doesn't help you decide when a given snapshot isn't needed anymore. For this I've created a simple script. Give the script your daily / weekly / monthly / quarterly / yearly snapshot retention policy and your snapshot list, and it will tell you which snapshots from the list you can safely delete.
This makes it simple to create and maintain snapshots with a retention policy from your own scripts. For various reasons, it is difficult to do this with the auto-snapshot service that is part of OpenSolaris.
Read more and downloadhere.