Simple to implement library by Todd Reed which will show touch point overlays on an external display. Combine this with the Reflection app that I linked last week and you have a top class solution for recording iOS screencasts and demos.
Gwynne Raskind writing for Mike Ash takes on rethinking the KVO APIs. I really hope that Apple give KVO some block based love in iOS 6, but until then this is well worth a look.
Mugunth Kumar on blocks, ARC and retain cycles. If you don't understand retain cycles properly, you very probably have leaks in your apps and this should be top of your reading list.
Mariano Abdala talks about the potential for abuse with audio only push notifications. I haven't heard of any apps that are using this maliciously but he makes a good point.