How could I copy the slide down effect with the tail on the springboard which occurs when a 'appgroup' (collection of apps in one folder) is selected?
It would be used to show a few buttons.
You can use simple Core animations to do that. Like so:
[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:2];
coverView.center = CGPointMake(coverView.center.x, 400);
[UIView commitAnimations];
Where coverView is a view covering your buttons, when this animation is executed the view animates to the point X=x Y=400 and uses 2 seconds to do it. You can do this to any object in interface builder, and therefore you can experiment and create what suits you. Hope that helps.