Matt Gemmell with some thoughtful words on really thinking about how a UI control gets its information and purpose across effectively using the lowly on/off switch element in iOS, Mac OS X and 3rd party apps as an example.
I really love browsing through UI mockups of apps that progress through development, such a great source of inspiration and insight into someones design process. Matt Gemmell (again!) generously shares some iterations on mockups while designing the new version of his Favourites app for iOS.
Great domain name for another site which showcases good quality iOS design. Unlike the last couple of sites like this that I have linked to, iOS inspires me focuses not only on app UI but also icons, websites and various other resources.