Mitch Resnick talks about why coding is for all
What Most Schools don't teach, probably the best promo for Computer Science I've seen:
Eben Upton talks about his personal mission to bring the Raspberry Pi to life
Whilst on the subject of the Raspberry Pi, I was very impressed by the girls from Charlotte Latin School
David Braben does a wonderful talk on Mathematics being beautiful illustrating the techniques used to create Elite and Minecraft
And finally Kate Russell talks about her IT career