Are you interested designing or developing your own iPhone Application or Palm Pre Application? Teehan+Lax has put together iPhone GUI PSD and Palm Pre GUI PSD to help designers pitch and develop polished concepts using a tool their pretty familiar with, Photoshop. The elements are built with vectors for easy editing and scaling.
iPhone GUI PSD: http://www.teehanlax.com/blog/2009/06/18/iphone-gui-psd-30/
Palm Pre GUI PSD: http://www.teehanlax.com/blog/2009/07/08/palm-pre-gui-psd/