I've been looking for some cool design template for iPhone/iPad or let's say iOS for a while until I found Teehan.
Teehan is a company located in Toronto, visit their page and be thankful to their brilliant work for this FREE PSD template. This template has also been updated to Retina version. That makes it the most powerful template! Some other site even sold $39 for a 3G version!
They also provides FREE template for iPad! Cool!
iPhone GUI PSD Design Template, v4.0 | Teehan+Lax
iPhone 4 GUI PSD (Retina Display) | Teehan+Lax