Change AppKit to appkit, but you will still won't find NSSpeechSynthesizer there.
if you need NSSpeechSynthesizer, try this:
from Cocoa import NSSpeechSynthesizer
sp = NSSpeachSynthesizer.alloc().initWithVoice_(None) # use default voice
sp.startSpeakingString_("hello world")
Cocoa should be part of the PyObjC as far as I can understand.
source: http://code.activestate.com/lists/pythonmac-sig/23406/