I was two years out of school working on C# and WPF when I was tasked with writing an iOS app. My first steps to gain knowledge of the syntax/structure/etc of the language was to watch the Standford CS139p lectures (http://itunes.apple.com/itunes-u/ipad-iphone-application-dev...). I only had to watch the first six or so before I had a good knowledge of the language and the starting point of UIKit. From that point I just started brute forcing it.
Reading Apple's documentation was the fastest way for me to ramp up and they actually include a lot of really useful examples. Even lower level things like CoreGraphics have some in depth examples which will probably be what you need for your "Flipboard" like interactions.
Because I do so much iOS dev I have my own "library" I now use for every project. But it was cobbled together over a couple years and inspiration was taken from many open source projects.
If you need to make web requests in your app (which basically every app should) ASIHTTPRequest is an interesting framework. https://github.com/pokeb/asi-http-request. I took the idea behind this and distilled it down to something that was much simpler which is what I needed. ASIHTTPRequest is sorta the kitchen sink of web request clients.
If you need a relational database in your app, sqlite is a simple include away. There are a lot of wrapper frameworks out there but I didn't use any of them. I wrote my first app directly accessing the C API and then wrote my own wrapper framework for it. Because I had never used SQLite before needed it in iOS it helped me learn a lot more about it.
One thing I'd point you to is my collection of Categories and Macros that I put into every project https://github.com/reidmain/Objective-C-Categories-and-Macro.... Specifically pay attention to FDIsNullOrEmpty, NSObject+PerformBlock, UIView+Layout. I use these categories so much that I always include them in my precompiled header file.
That's all good advice, but I'd like to point out that ASIHTTPRequest has been abandoned for about a year now. I think most people have switched to using AFNetworking (https://github.com/AFNetworking/AFNetworking) which came out of Gowalla.
As a nice bonus, AFNetworking doesn't require you to implement delegates but instead allows you to use blocks, which simplifies things somewhat.