A book entitled _Can Reindeer Fly? The Science of Christmas_ by Roger Highfield attempts to tackle all those tough questions asked by the discriminating child with no appetite for trite answers to those inevitable "How does Santa do that?" questions. Highfield supplies some scientific explanations for the feats of St. Nicholas.
Notably, Highfield proposes that Santa doesn't need to carry two million tons of presents on his sleigh, because they can be built in the house of each child's house by molecular assemblers. I guess that gives a new meaning to the term "Santa's elves". :)
Some other Highfield explanations:
The Immaculate Conception: Highfield speculates about Parthenogenesis but concludes Mary Magdalene must have been a hermaphrodite (making the book a gift idea for that special Catholic friend).
Santa's Sleigh: An awesome machine capable of speeds of Mach 6,395 which generates sound waves that are exactly out of phase with sonic booms to mask its supersonic bursts.