Cocoa Controls – cocoacontrols.com is a great place to find UI for iOS and OS X. There are more than 2000 open source and commercial UI components for programmers.
The main goal of this resource is to help developers improve the quality of Cocoa applications with the least work possible.
Project Cocoa Controls created by 2 people : Aaron, a software developer and photographer in Seattle and Rob – a software engineer by day and radio amateur by night.
Give it a try at cocoacontrols.com