AWESOME science youtube channels:
To help you study or understand concepts from class better:
The Amoeba Sisters - they explain things quickly, simply, and in a fun way.
Physics Girl (she explains things well but also does some pretty cool experiments)
Khan Academy- they have entire lectures on topics we've covered in class-- and SO MUCH more
Crash Course- They explain things quickly and effectively. I think Amoeba Sisters does a better job though.
To make you think about cool new things (or maybe just see some cool explosions):
The Backyard Scientist (He does the craziest experiments! If you want explosions look here)