This can be a bit of a tricky question to answer, as most celebratory elements of Christmas have more to do with ethnic culture than religion. As an example, while both Italy and France are Catholic, only Italy has Dominic the Christmas Donkey.
On Christmas Eve there is a Vespers service in the evening (some monasteries may have an all night vigil, something not uncommon before a major feast), and then on Christmas Day there is Divine Liturgy in the morning.
For Orthodox Christians in Ukraine, the night before Christmas is known as Sviata Vechera
or Holy Supper. On this evening, a 12 dish meatless and dairy free supper will be served. Each dish representing one of Christ's apostles. The meal begins after the first star is seen in the night sky, or after evening Vespers. This represents the three magi who were led by a star.
Wheat will be placed under the tablecloth to remind us that Christ was born in a manger. After dinner, the family will usually sit around the table and sing Christmas carols.
More information can be found here
As an American Orthodox Christian of Ukrainian descent, like most Americans, my family borrowed traditions from our ancestor's heritage and mixed them with other American traditions. I grew up with a Christmas tree, the myth of Santa Claus, watching "Rudolph the Red Nose Reindeer," and singing American Christmas carols. Due to the fact that my family's parish is "Old Calendar," December 25th was reserved for Santa and Presents, and January 7th was when we focused on Christ's Nativity, went to Church, and had a traditional Ukrainian meal.
A few years ago, my sister, who lives several hours away from the rest of the family, could not come home for Christmas because she was on-call for work. (She works as a Cardiac Ultra Sound Technician at a hospital.) My parents and I traveled to be with her, so she wouldn't be alone for Christmas. The parish she was attending was a New Calendar Greek Orthodox parish, and celebrated on Dec. 25th. When we went to Liturgy Christmas morning, we were surprised to see most of the pews were empty. The majority of the parishioners had come the night before for vespers, and were spending Christmas morning opening presents with their family.
Now, is this how all Greek parishes are? I don't know, I can only share with you my experience.
At home, the Ukrainian Orthodox parish I attend is generally light in attendance for Vespers, but a full house on Christmas morning.
You also ask which feast days the Protestants god rid of, to which I answer, which group of Protestants? Remember, not all Protestant groups are the same.
The Anglicans have a full Liturgical calender, and celebrate a different saint or feast every day. (Just as the Orthodox Church does.) The Lutherans also have a liturgical tradition, but I'm not familiar with the details of their feast calendar.
It's also important to remember that the Protestant Reformation was a rejection of the Roman Catholic Church, so any feast days they disposed of would have been from Rome's calendar, not ours. Although there are feasts that the Orthodox share in common with Rome, not all are the same, nor do all fall on the same dates.
For the Anglicans and Roman Catholics, the 12 days of Christmas known as Christmastide start on December 25th with the birth of Christ, and end on January 6th with the Feast of the Arrival of the Magi.
In the Orthodox Church, Christmastide begins with the Nativity of Christ, but ends with the Feast of Holy Theophany, when Christ was baptized in the Jordan and the Trinity was revealed. In fact, at one time these feasts were celebrated together, and the second feast is seen as more significant than the first. (However both are important.)
Now, in between the Nativity of Christ and Theophany, you also have the Synaxis of the Theotokos (which is when we honor Mary for her role in the Incarnation), the remembrance of St. Stephan the Protomartyr, the remembrance of the Holy Innocents (when we remember the children who were killed by Herod's sword), the Circumcision of Our Lord (which also falls on St. Basil's day), and the Synaxis of the Holy Apostles. The week after Christmas is also a fast-free week. (It's amazing how much joy people receive from being able to eat a hamburger on a Wednesday! lol)
You can learn more about the feasts of the Church by spending some time in the Greek Orthodox Archdiocese of America's Online Chapel
. There you can read about all of the feasts and fasts of the Church, and their meaning.