I use YouTube for instructional videos, especially DIY projects and baking ideas.
I also use it for book reviews and finding interesting things in general.
I also use it as a great stress-buster, especially stand up comedy.
I use youtube to watch
1 Indian classical music videos
2 TED talks
3 Interviews of Writers, Motivational speakes, classical Musicians Lacture Cum Demonstrations etc
I primarily use youtube for watching old music videos.
Being somewhat of a time-warped guy I listen to music that I listened to as a student
I am pretty old by the forum members standards!
Then there are the instructional videos on getting things done on your PC/phone, DIY repairs
and ocassionally reviews of gadgets that I am considering buying or recommending to others.