HDR method using a single RAW file.
Trying to explain this to anyone is a great lesson in futility. They say that a picture is worth 1000 words, and I believe it.
Take a look at these images for detailed instructions on how to create and seamlessly blend multiple exposure zones from within a single RAW file using Photoshop and Adobe camera RAW.
I just want to note here that I only use a highlight layer for this example. You could also use this method to bring detail into shadows. In an extreme case you would want to make a layer for shadows, mids and highlights. Also, RAW files are not infallible. If the highlights or shadows are too far gone, nothing but a second file/exposure is going to work.
These images are read from left to right, top to bottom.