Jon Peddie Research has written a paper on digital file formats (DV, MP3, JPG, and so on). The purpose was to find out how much disk space is needed by each format. I found the article interesting, because it also discusses some of the technical aspects of each format.
For example, did you know that DV (digital video) format uses 5:1 compression?
The paper makes some statements I would disagree with, such as the average size of a JPG: they say 1.3MB, I say 400MB. You can download the document from Memory Capacity Requirements for Media Files.