This is a collection of interesting and useful websites for iOS development, as well as some more general technical stuff.
General
Apiary
If you deal with REST APIs, this is some pretty neat stuff:
http://apiary.io
Quandl
Tons of numerical datasets. Not sure what I’m going to do with this, but I feel like I should come up with something:
http://www.quandl.com
Xcode Tools
XCode Package Manager
An easy way to manage adding packages that modify and improve Xcode.
http://mneorr.github.io/Alcatraz/
Snippet Editing
This is a nice tool to let you edit your Xcode snippets.
http://cocoaholic.com/snippet_edit/
Appledoc
If you are looking to document some Objective-C classes or frameworks you’ve created, this is a very easy way to generate documentation that looks like Apple’s. This tool can also create documents that will integrate nicely with Xcode as well.
http://gentlebytes.com/appledoc/
Objective-C
Objective-C Features
Wondering when a certain feature was available in Objective-C? Wonder no more!
http://developer.apple.com/library/ios/#releasenotes/ObjectiveC/ObjCAvailabilityIndex/index.html
Classes, Frameworks, and Libraries
Networking
This makes networking so much easier it has to be see to be believed. There are many large and serious iOS apps and products that make use of this class!
https://github.com/AFNetworking/AFNetworking
Core Data
https://github.com/magicalpanda/MagicalRecord
Handy Classes
This is a collection of very handy-looking classes for iOS development.
http://sstoolk.it
Sliding side-panels
https://github.com/ktatroe/sidepanel-ios
JKFiltering
Filter arrays with blocks
https://github.com/jklaiho/JKLFiltering
Numeric Entry
https://github.com/benzado/HSNumericField