I was out walking the other day and flushed a Barn Owl which had been perched in an Ash tree.
When I looked around the vegetation below the tree I found this pellet.
I put some water in a shallow dish and soaked the pellet for a couple of hours and then using a pair tweezers I separated the bones from the fur. I then allowed the bones to dry and glued them onto a piece of card.
There is a really nice site here with a key to identifying skulls.