- Research Assistant within Xcode: provides context sensitive help for the iPhone SDK. Move your mouse over something from the framework (ie. UITextField) and see the accessors, mutators, protocols, etc. associated with that datatype.
- Stack Overflow: a question and answer site for programmers by programmers. If you don't know of it and you program you need to know of it. Check out this Q&A for a list of top blogs/sites about iPhone Development: http://stackoverflow.com/questions/232570/what-are-the-best-cocoa-touch-iphone-programming-blogs
- Apple Developer Connection iPhone: of course going to the source is one of the top choices. Check it often for updated docs.
- Apple Developer Forums (Beta): another great resource in line with Stack Overflow, ask your question and get an answer. But remember, try to figure it out yourself first, if you don't know this you will find out the hard way.
- Standford University's iPhone Application Programming: mentioned in previous post, this is another great resource for sample code and explainations Standford University's CS193P iPhone Application Programming.
- Apps Amuck Blog: Not bad if you are just starting out and want to learn how someone else wrote some apps which are in the AppStore. Check their 31 Days of iPhone SDK Apps for lots of sample code.
Do you have a site that you find useful in day to day iPhone programming? A great repository of sample code? A write-up on how someone else wrote their program and got it launched? If so drop a comment, I'd love to hear about others.