FastImageCache
iOS library for quickly displaying images while scrolling
...In order to understand how Fast Image Cache works, it's helpful to understand a typical scenario encountered by many applications that work with images. iOS applications, especially those in the social networking space, often have many images to display at once, such as user photos. The intuitive, traditional approach is to request image data from an API, process the original images to create the desired sizes and styles, and store these processed images on the device.