Christmas was a huge holiday. Many religious holidays were outlawed after the Church of England split away, but Christmas was a large celebration that often shows up in literature, like Sir Gawain and the Green Knight. In that story, noblemen are feasting, listening to stories, and watching duels that are either good-natured contests between friends or reinactments of old battles. In reality, their festivities had many of the same customs as today. People would feast, sing Christmas carols, decorate their homes with holly or ivy, and get the biggest log they could (called the Yule log) to burn in their fireplace. Christmas carried through until Epiphany (the twelve days of Christmas), which is the day when the wise men brought Christ gifts twelve days after his birth.
They had a lot of other holidays: Plough Sunday, Candlemas, St. Valentine's Day, Midsummer, Lammas--a feast to St. Peter, Michaelmas, and Easter.
Shrove Tuesday was another huge celebration. It was the last day before Lent began, so they would get all the celebration and feasting in they could before the more serious season started. Today this is Marti Gras. The holiday came with jousting tournaments and feasts among the upper class, chasing greased pigs, bear baiting, cock fights, and the ever-popular contest to see who could climb a greased pole. If you wanted to chnage your luck, you could even try to smash your pottery and see if that smashed any bad luck you'd been carrying around.