Mark Johnson, who is (among other things) an iPhone developer and also teaches iPhone programming classes, has posted a great blog entry on asynchronous downloading of images into a table view. Asynchronous networking is one area that a lot of readers have expressed an interest in and confusion about, and it's also one topic that we don't cover in the book. Mark's blog post is a great place to go if you're confused and/or interested. It's clear, well-explained, and uses a very practical example to illustrate its points. If you're confused by asynchronous networking, it's well worth your time to stop by his blog.
While you're there, check out Mark's iPhone applications: Hit Tennis and Smart Caller.