I'd like to introduce a new open source framework that I've written, called GPUImage. The GPUImage framework is a BSD-licensed iOS library (for which the source code can be found on GitHub) that lets you apply GPU-accelerated filters and other effects to images, live camera video, and movies. In comparison to Core Image (part of iOS 5.0), GPUImage allows you to write your own custom filters, supports deployment to iOS 4.0, and has a slightly simpler interface. However, it currently lacks some of the more advanced features of Core Image, such as facial detection.
Read on for more about the GPUImage framework.