Not exactly a small creature but I have been watching a robin build this nest in the crabapple tree this week. It will hopefully be filled with baby robins in a few more weeks. While the builder was away, I snuck a peek and photographed the nest under construction. The interior was filled with fresh mud which appeared to be spread evenly all around the nest's interior.
UPDATE: Becky and I peered into the nest a couple of days later and found the inside lined with grass and a single BIG blue egg inside. We thought the egg seems larger than we remembered. Mother robin appears to be content. I later noticed two baby robins peering out from under the mother robin one day.