A List Apart had a nice article on accessibility and the importance of real-world user testing. And for some reason dasBlog is tripping out on me.

Here's the link: http://www.alistapart.com/articles/workingwithothers/

The article has some nice tips, like viewing your web site in IE6 with the font size set to "Largest" to make sure that your fonts all scale up correctly. But the comments also had some gems, for example a link to this paper about observations of screen reader users and how they navigated sites. Craig Francis also listed a huge number of notes from a recent presentation he was at, with some interesting insights.