Huni (King Hu) is considered the last king of the 3rd dynasty. He is placed right in front of Sneferu on Turin King List, who was the founder of the 4th dynasty. He might rule for 24 years according to this list, but there's no evidence for it today.
Huni (King Hu) was apparently the first Pharaoh, who began with writing his name in cartouche - an oval, that symbolized an endless rule of a Pharaoh and Gods. It became a tradition later, till the Roman period, so it had lasted for almost 3,000 years.
We have most information about the end of the 3rd period from the tomb of Huni's state official. In this period a big economical advance in property relations is visible compared with the traditions of the first three dynasties. Till the period of Huni, the Pharaoh was the only owner of the land and everything in it, but it turns out, that even common people (even if in high positions) could own large legal-acquired property at the end of the 3rd dynasty.
Two pyramids of the pharaohs.