Here is a list of the Nobel Laureates per university straight from the source (based on affiliation at the time of the Nobel Prize announcement):

http://nobelprize.org/nobel_prizes/lists/universities.html

Wikipedia has another list based on what universities claim themselves:

http://en.wikipedia.org/wiki/List_of_Nobel_Laureates_by_univ...

So while Caltech is doing very well indeed, there are 15 universities with more affiliated awardees.