Images and UITableViewCells and Objective-C key paths
Here are two wonderfully useful articles by the folks at Probably Interactive on Images and UITableViewCells and Objective-C key paths.
The first article describes a method of loading images into table view cells while keeping the UI responsive using threads (you can also do the same thing using NSOperation/NSOperationInvocation and NSOperationQueue but it was instructive for me to see the threaded approach). The article also has a fully-working example that you can download and play with. (And while you're at it, also check out the atebits article on how to render your table view cells for maximum performance.)
The second article is on key paths. If you're missing some of the ease of working with data structures in languages like Python, you might be positively surprised by the power of key paths.
Here's a thank-you to the Probably Interactive folks for writing these up.