GIFit! - Quickly turn YouTube videos into GIFs (chrome extension)
Yout - YouTube to Mp3 Converter
Turn Off the Lights - With a single click on the lamp button, the page will fade to dark.
Softorino YouTube Converter - Download YouTube video & audio. Watch and listen offline
Youtube Plus - Home of the extension YouTube Plus that allows you to experience more on YouTube - ParticleCore/Particle
You-Get - Command-line utility to download media contents from the web