I recently installed gaug.es on my site (which is totally awesome). I noticed most of my traffic goes to blog posts that are decently old. At the time they were accurate and the stuff I mentioned was, at the time, the best practice.
It's funny how quickly things change in the software world. A blog post less can be super horrible advice less than a year later. That's why I never recommend a book to someone wanting to learn Rails. That stuff changes constantly. I still think Aaron's books on iOS programming or Mac programming are really fantastic. I learned with his book on Mac programming before iOS came out. (He has a book on Objective-C too. I haven't read it, but I'm sure it's fantastic.)
Objective-C doesn't change nearly as much as the Ruby world does. Recently we've gotten Objective-C 2.0 (plus the advancements in the Apple LLVM compiler) and ARC. Everything is always backwards compatible without making things too crufty. It's really amazing how well it's held up. More on all of this later though.
Here's a list of some of the posts I updated: