If you have to read lots of material in the daily course of your work, e.g., in email, news on the web, general web surfing, then you will naturally learn to speed-read. I've taken a speed-reading course when I was younger, but I don't know if I'm reading fast now because of, or inspite of, that course.

Similarly, I naturally learned to type fast in the course of using the computer at work. I can, for example, attribute some of my typing skills to my years of programming.

Regarding comprehension, I've found that my comprehension on a material I've just read is directly proportional to my interest in the topic at hand. For example, I can read quickly, comprehend and recall accurately minute details of an article about my favorite car.