Giants, as of this month the market share for each OS appears to be:

SymbianOS has 32% - This is for "dumb" phones... Mostly Nokia.

IOS(apple) 23%

Android(Google) 21% - This is what Nunchi was demonstrated on

BlackberryOS 10% (RIM)

SamsungOS 5%

There is also OS's out there that can not be detected, that appear to have about 5% of the market.