A while ago I was going over some videos on YouTube.com looking for different drawing techniques and I came across quite a few speed drawings (paintings). For those of you who don't know what speed drawing is, the simplest explanation is to watch one. I don't know the exact definition of the term, but from what I know it's the action which involves the filming of an entire drawing process, playing it at high speed and completing it with an appropriate sound track. The result is a very good insight in how these people work and a very good knowledge resource.
As I said, the videos show you almost the entire drawing process, so you can see how sketching, coloring, shading and highlighting is done. If you want to start learning drawing or even if you are looking to improve your skills, these show you how certain things can be done. They don't beat a drawing class, but they're a good intro and even a better motivation tool.
If you look around on the Internet you'll definitely find all sort of websites dedicated to this form of art, some might call it. One of my favorite is http://www.speed-painting.com. The website owner is Nico Di Mattia and that's the place I've seen some of the best videos. On YouTube (probably even on other video sharing servers) you can find speed drawings of artwork created in the almighty Adobe Photoshop, but you can find some that are real amazing, like the one I've embedded below. It's entirely created using MS Paint. That's right, the lame one that comes with Windows. Just watch the video and you'll see what someone with proper skills and a lot of patience can achieve.