These people on YouTube have made this series, designed to spread and promote Scientific literacy and interest.
I think they're still ongoing, maybe uploading one every week or so.
Each one is quite short.
These are the Feynman series:
http://www.youtube.com/watch?v=cRmbw...eature=related
http://www.youtube.com/watch?v=Dkv0KCR3Yiw&feature=related
http://www.youtube.com/watch?v=lmTmGLzPVyM&feature=related
Sagan series:
http://www.youtube.com/watch?v=oY59wZdCDo0&feature=related
http://www.youtube.com/watch?v=j2oXFWKpJiA&feature=related
http://www.youtube.com/watch?v=gCfemmxqaRg&feature=related
http://www.youtube.com/watch?v=zxsJeND_D-k&feature=related
http://www.youtube.com/watch?v=EHuve33yOVY&feature=related
http://www.youtube.com/watch?v=3wJYpRJQVbo&feature=related
http://www.youtube.com/watch?v=drAWo_zFh8M&feature=related