Now that Apple is requiring launch images in all iOS apps, many developers will see their application size increase, perhaps drastically. I use a fantastic (and free!) tool called ImageOptim to reduce the size of the images in my projects.
I was able to get over 65% file size reduction on my iPad launch images, and well over 50% on the iPhone images. Of course, your mileage may vary but it’s certainly worth checking out.
ImageOptim isn’t limited to iOS apps. It’s useful wherever you may have a need to for reduced PNG file sizes.