Via Teaching College Math, I discovered Math TV, which provides videos of worked-through high school level mathematics problems.
There are two sites: MathTV, which has problems presented by a couple of different people, and a YouTube site, which contains a lot more problems, all of which seem to be presented by the same guy.
That's OK, because I think he does the best job, anyway.
Unfortunately, they've disabled embedding, but click on the image for a nice example of integration by substitution ... although I think the last one could have been explained more simply than by using polynomial long-division!
All up, a nice resource.