Scratch (2001) is a documentary film, directed by Doug Pray, that looks at the birth and evolution of hip-hop disc jockeys (DJs), scratching and turntablism.
Interviewees include:

Grand Wizard Theodore (the inventor of the scratch)
Grand Mixer Q-bert
Grand Mixer DXT, Z-Trip
Mix Master Mike
Rob Swift
DJ Premier
Afrika Bambaataa
Jazzy Jay
Cut Chemist
NuMark
DJ Craze
DJ Shadow
DJ Babu
DJ Krush
Madlib
Peanut Butter Wolf

You can watch the whole [...]

Jesse Kriss and DJ Axel Foley have put together an interesting collection of Visual Scratch videos:
We capture turntable velocity using Ms. Pinky and fader position using an Ecler Nuo 4. The scratching sound is generated in Max/MSP. Then we scale the control data (turntable and fader) to ±1.0, the range of digital audio signals. The [...]