CreateJS is a suite of modular libraries and tools which work together to enable rich interactive content on open web technologies via HTML5. These libraries are designed to work completely independently, or mixed and matched to suit your needs. The CreateJS Suite is comprised of: EaselJS, TweenJS, SoundJS, PreloadJS, and Zoë.
I really like PreloadJS, which makes it easy to preload your assets: images, sounds, JS, data, or others. It uses XHR2 to provide real progress information when available, or fall back to tag loading and eased progress when it isn’t. It allows multiple queues, multiple connections, pausing queues, and a lot more.
License: License Free