A similar question: how do you make an app ONLY support landscape?
This method was used in the answer above:
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
if (interfaceOrientation==UIInterfaceOrientationLandscapeLeft || interfaceOrientation==UIInterfaceOrientationLandscapeRight)
return YES;
return NO;
}