A friend mentioned in passing that Nottingham University, UK had standardised on the Verdana font because it was the easiest for dyslexics to read. I had never heard that Verdana was a good font to use before but I had previously looked at Read Regular, a font design especially for dyslexics. Personally I don’t like it but this might be to do the web site’s background pattern that I find very hard on my eyes. Advice on dyslexia friendly fonts and general layout can be found on the British Dyslexia Association website and on Dyslexic.com. TechDis who appear to do research in this area have a comprehensive guide to style and fonts for website [PDF]. The results of a study of reading speeds and subjective preferences show that Verdana was the best font but this wasn’t specifically limited to dyslexia.
You can try out the effect of fonts, alignment and contrast on readability in this online experiment.