To help streamline your iPhone app design and development, we have put together a fairly comprehensive collection of iPhone & iPad GUI kits that will allow you to focus on developing rather than having to design everything from scratch.
There are 160 clean and simple toolbar icons in this set designed specifically for the iPhone, with a source .psd file for futher customisation.
iPhone Toolbar Icons »
The Glyphish icon set have designed and carefully optimized specifically for use on toolbars and tab bars in iPhone apps, but would also be perfect for Android Development.
The 130 icons are 24-bit .png images are about 30×30 pixels for tab bar icons and about 20×20 pixels for toolbar and navigation icons.
This set of 64 icons for the iPhone toolbar that contain beautiful shaded portions to give added depth and to highlight the icon features.
iPhone Toolbar Icon Set »
These icons have been developed specifically for iPhone developers, completely free for anyone to use commercially under the Creative Commons Attribution 2.5 Canada license.
Free iPhone Toolbar Icons »
iconSweets is a free icon set containing 60 vector Photoshop shapes, influenced by icon sets such as Glyphish and Pictoico. Perfectly suitable for iPhone & iPad app development.