Some of the earlier reports have alluded to problems the physically disabled may have in accessing information over the Web, but "Achieving E-Government for All" is the first to discuss this issue at any length.
I think it's easy for most of us to forget that the Web is not always kind to the disabled. On the Web we imagine that it shouldn't matter what you look like or if your body is weaker in some ways than other people, but many popular Web design elements shut out whole segments of the population.
When I was in high school I had a friend who was blind, and she used e-mail and chatted on local BBSes. However, this was in the "old days". Most online content was just text and you used typed commands instead of a mouse. It was possible (if a bit slow and awkward) for a blind person to participate in the online world if she had a Braille keyboard and a text-to-speech synthesizer. Today, a blind person is at a much greater disadvantage online. As I'm typing this post I can see all kinds of buttons and icons on my screen that I could click on to do different things, but people who are visually impaired may find it difficult or impossible to interact with a visual-based setup like this.
A group whose needs are often ignored when it comes to web design is the color blind. Printed text is almost always black-on-white, but on the Web it's possible to make the text and background almost any color. Certain color combinations will result in a page that's illegible to a color blind person. Some color combinations are difficult for anyone to read (especially if their monitor is old and dim) but are chosen for aesthetic reasons without regard to legibility. In the early days of the Web I remember seeing a lot of pages that were dark magenta on light magenta or light blue on dark blue, and I had to highlight the whole page in order to read it. Government websites typically use more conservative color schemes, but there may still be problems with banner headings or buttons.