Blue Mangoo released Tube AU, an AUv3 plugin for YouTube content. They have to be very careful about how they market this... but I don't! This is going to be a boon for anyone that wants to sample from YouTube videos! Just plug this into your AUv3 host and you can then record YouTube audio into your AUv3 arsenal.
Tube AU iTunes Description:Tube AU is a web video player audio unit plugin.
The plugin user interface looks like an ordinary web browser but there are some small differences. First, the audio stream is sent to the audio unit plugin output. Secondly, the browser is limited to viewing only YouTube.
This is useful for processing audio effects on YouTube videos. For example, you can use a pitch shifter plugin to change the key when singing karaoke, or test compressor plugins on professionally mixed music.
Note that this is an audio unit plugin only; it does not run as a stand-alone app.