I know some people who are interested in getting into iPhone application development. There is a lot of advice out there. Here's my advice for experienced developers who start out knowing nothing about iPhone or Cocoa development:
- If you don't know the C programming language, learn it.
- Read Matt Gemmell's "iPhone Development Emergency Guide".
- Buy and read iPhone SDK Development by Bill Dudney and Chris Adamson. Also buy and watch the Xcode- and iPhone-related screencasts available from that web page.
After that, you'll be able to delve into the other things you need in Apple's documentation. I'd recommend learning all you can about Core Animation and Core Data, but it depends a lot on exactly what kinds of apps you want to write.
Finally, write lots of little iPhone apps before you start on that big important app you really want to write. The language and tools are a little strange at first, but the more you use them, the better they feel.