So there is a youtube channel that I really love called : The Periodic Table of Videos. (Clickety clic)
It is a collaboration between the University of Nottingham's School of Chemistry and video journalist Brady Haran. They present the 118 elements of the periodic table in videos and started a great series about molecules as well.
The series' staff is full of great personalities, and among them the famous Professor Martyn Poliakoff who is really an amazing person. Here is a little funny portrait that I made of him.
Other great science channels :
Backstage Science : A series that bring us inside of some of UK's most amazing science facilities, like the STFC's Vulcan laser, or Diamond Light Source's ISIS...
Sixty Symbols : "A channel devoted to those funny letters and squiggles used by physicists and astronomers."