MSVC++ 2008 although I do still have DevC++ 4.992 installed I use it for test programs and like said above its handy for small single file programs too.
I did have code::blocks but uninstalled it. And I agree with Bubba, 2003 is "deceprecated" as MS themselves like to put it I have had 2005 too at one point and found it to be good, I upgraded to 2008 at the turn of the year.