In a follow up to this article from a couple of weeks ago, Radek Pietruszewski has put together a great article taking the technique even further. Even with the announcement of the native SDK next week, all networking is still going to be across the connection with the phone so techniques like this are important.
This one doesn't need much explanation. Ever had to look up an error number for an Apple API? The answer is here, all in one place.
Yannick Loriot with a useful little library. It's really common to need to adjust a colour lighter or darker and I've been using a couple of small functions to do this in apps for a while now. This library does that, and more including inverting colours, saturating/desaturating and complimentary colours. Useful.
Marin Todorov with a new animation library. It doesn't stray too far from the standard UIView/CALayer animations but does allow the two to be mixed together which can be really useful. It also includes spring animations for layers and the ability to chain animations together. Looks really good.