Since April 2013 Youtube has a feature “Youtube-Mix”. From what I could find out searching the web, these lists are auto-generated based on the video you are currently watching.
For instance, when I watch Soha's song “Mil pasos” I get this playlist suggestion. Or, if I start from RAHJ's “15 minutes”, then this playlist comes up. Or, if I start from Holly Golightly's Virtually Happy, I end up at this playlist.
I like them very much. I wonder how these lists are generated. Since this is Google, I suppose there is some smart algorithm at work, not hand-crafted lists. But which features does this algorithm use?