Open Source

Built atop AFNetworking, it rips through JSON asynchronously to give you ready-to-use Instagram model objects – @bhatthead

Collection of iOS open source UI controls – @soffes

I previously introduced ReactiveCocoa. If you are looking for a good introduction, Ray Wenderlich has a two part tutorial that may be of interest. ReactiveCocoa Part 1 and Part 2

For the uninitiated:

ReactiveCocoa is an Objective-C framework that provides APIs for composing and transforming streams of values. By chaining, combining, and reacting to signals, software can be written declaratively, without the need for code that continually observes and updates values.

Ross Gibson is the author of TTCounterLabel:

A custom UILabel that acts as a time counter, counting up or down and formatting the string to hours, minutes, seconds and milliseconds. Designed to accept a value in milliseconds that is then displayed it in a time friendly format.

Brushes, an open source painting app written by Steve Sprang:

An accelerated OpenGL-based painting engine makes painting smooth and responsive — even with huge brush sizes. Brushes also records every step in your painting. Show off your creative process by replaying your paintings directly on your device.

The binary version of the app is available in the App Store.

Johnny Wu is the author of JYRadarChart, an open source project that displays charts that mimic a radar display. The screenshot below shows an example:

Robert Böhnke on his block based animation project:

RBBAnimation is a subclass of CAKeyframeAnimation that allows you to declare your animations using blocks instead of writing out all the individual key-frames. This gives you greater flexibility when specifying your animations while keeping your code concise.