Yellow Sale on mathematical books is here. I made the mistake of stopping by the book store in the student union (for a completely non-book-related errand), saw the sale signs, and walked away an hour later with Brenner and Scott's The Mathematical Theory of Finite Element Methods and a big smile. I almost got Marsden and Ratiu's book on symmetry in mechanics, too, or Osher and Fedkiw's level set book. But I resisted temptation.
Hooray for books!