The Queen has praised the "army of volunteers" at the Diamond Jubilee and the Olympic and Paralympic Games.
In her Christmas message, she said it was striking to see the "friendship" of so many people who marked her Jubilee, particularly during the river pageant.
She said the pageant on the Thames on a wet, cold day in June with 1000 vessels showed a "determination to celebrate triumphing over the elements." An estimated one million people were watching along the banks.
She earlier attended Christmas service at St Mary Magdalene Church in Norfolk.
The Queen's message, broadcast in 3D for the first time, was interspersed with footage from the large-scale events in Britain in 2012.
"This past year has been one of great celebration for many. The enthusiasm which greeted the Diamond Jubilee was, of course, especially memorable for me and my family.
''It was humbling that so many chose to mark the anniversary of a duty which passed to me 60 years ago,'' she said.
"People of all ages took the trouble to take part in various ways and in many nations. But perhaps most striking of all was to witness the strength of fellowship and friendship among those who had gathered together on these occasions."
Army of volunteers
She praised the large contingent of volunteers who adopted many roles during the Olympic and Paralympic Games, held in London during summer.
"We were reminded too that the success of these great festivals depended to an enormous degree on the dedication and effort of an army of volunteers.
"Those public-spirited people came forward in the great tradition of all those who devote themselves to keeping other safe, supported and comforted."
The Queen said that for many - particularly the Armed Forces, emergency services and hospital workers - Christmas was a time for serving others, and being away from loved ones.
Her grandson, Prince Harry, is currently serving as an Apache helicopter pilot with the Army Air Corps in Afghanistan.
"And those who have lost loved ones may find this day especially full of memories. That's why it's important at this time of year to reach out beyond our familiar relationships to think of those who are on their own."
She recalled the Christmas story of the birth of Jesus, saying: "It is my prayer this Christmas Day that his example and teaching will continue to bring people together, to give the best of themselves in the service of others."
The BBC's Royal correspondent said the address was a classic Christmas message, making use of strong images and powerful emotions, rounded off with the essential Christian message of humanity and caring for others.