Core Data iCloud sync without Core Data iCloud sync. I first linked to this framework from Drew McCormack in October last year but it reached a 1.0 this week. For me, the big benefit is that the whole system is much more transparent than true iCloud sync which should make debugging easier, not to mention access to the source code so you can see what's actually going on. Add in support for different remote data stores and this looks excellent. Congratulations on 1.0!
Ever thought that writing transform code is a bit long-winded? No? Then let me ask you if you have ever written any non-trivial transform code? Jonathan Wight has put together a small DSL which allows composite transitions to be built up in a much more concise way. If you're writing code with any significant number of transforms then this might clarify and will certainly reduce the transform sprawl.
Reynaldo Gonzales with a concise library to assist in validating JSON before allowing it into your precious objects. Simple but just like Transformer-DSL above, this has the potential to simplify lots of repetitive code in your models.
It's hard to keep up with all of the quality content that Brent Simmons is posting recently, you should go and subscribe directly. This article is great as always, but I'm linking to it more because of why he wrote it. Brent recently talked about writing down your problem as a method of solving it on Episode 75 of the Talk Show and this is clearly him doing exactly that. It's like a better version of Rubber Duck Debugging because you don't feel anywhere near as stupid when you write it down 😄. You can just hear the gears click into place when that last line of the post gets written, "I think it’s a win, and not much work. I’m going to do it."