iosdeveloper/LaunchImageTransition

Fades from your launch image (Default.png) to root view controller. Lets you choose the transition animation and delay.

Just copy both LaunchImageTransition.h and LaunchImageTransition.m to your project.

Don't forget to #import LaunchImageTransition.h in your app delegate.

Replace
self.window.rootViewController = self.viewController;
with
self.window.rootViewController = [[[LaunchImageTransition alloc] initWithViewController:self.viewController animation:UIModalTransitionStyleCrossDissolve delay:1.0] autorelease];

Animation has to be one of the UIModalTransitionStyles, Delay is optional.

Please take a look at the project for an example implementation.