The process for provisioning devices to deploy iOS apps has often caused confusion, or downright dismay. As versions of iOS have rolled on, the process has gotten easier, but there's a lot of old information and misinformation out on the web.
An increasingly common activity in iOS apps is retrieving data from web services. This is particularly true when the app is really an extension of the functionality offered by a web-based application. One challenge in doing this is that some key classes often used in Mac OS X applications are not available on the iOS platform: specifically, NSXMLDocument. This turns out to be a blessing in disguise because NSXMLDocument is not very performant. Instead, I use TBXML, an excellent lightweight XML parser.
A lot has changed in Xcode 4. As I recently worked on implementing some web services, I needed to add the libxml2 library to my project.