Reindeers were intelligent, fast, and excellent talking beasts in Narnia.
The ones that pulled the White Witch's sled were White Reindeer, which were either her followers, or her slaves. Brown Reindeers, however, were on the side of good, as they pulled Father Christmas's sleigh.
Reindeer were mentioned in the second of the Chronicles of Narnia books, The Lion, the Witch, and the Wardrobe.
The brown reindeer are mentioned as being larger than the white ones.
The reindeer in the book appeared to not be able to talk, although it was never mentioned one way or another. If the reindeer were, in fact, non-talking beasts, then they would have been neutral, rather than taking the side of Aslan or the White Witch.
| Movie-based Information|
There were some reindeers seen in the first two films. The first obvious ones were the those that pulled the sleighs of Father Christmas and Jadis.
There was one shot of another reindeer or Stag in The Chronicles of Narnia: Prince Caspian (film), which was outside Aslan's How, watching as all the other Narnians returned from the Battle of Miraz's Castle.