How do I feel about this one? Conflicted. I am usually suspicious of libraries where you need to adopt a full new set of controls as you have the potential to lose things like accessibility support and risk introducing a slew of edge case bugs. However this library by Tom Benner is worth a look because he is just subclassing the UIKit controls and adding styling using pretty solid iOS techniques and it does have the potential to remove a lot of UI code.
Neat little set of classes for cleaner KVO and simple bindings by Jamie Montgomerie. Every time I write observeValueForKeyPath: I think I should write something like this. The good news is that now I don't have to because Jamie did.
There has been a fair bit of talk over the last few issues about UIActivity. Even though this is going to attempt to stay away from becoming UIActivity weekly, I wanted to link to this post by Mariano Abdala on designing a better UIActivity API which might save you a little time and code when implementing your own activities.
Auto Layout ported back to iOS 5? Coded for relaxation (yes, really) after shipping an app by Rolandas Razma this is an interesting experiment which might be useful if you are supporting iOS 5. I remain completely unconvinced on Auto Layout myself but if you are in that set of Auto Layout lovers this may be of interest.