For the past 6 months or so the lab I work at has been working on a system to administer studies and surveys related to autism. We wanted something more customizable than something like SurveyMonkey, so I was tasked to create our own version.
You can see the result at http://thegatewayproject.org
Usability was extensively tested and geared towards autistic and disabled, so the design and layout is very simple.
Note: by default, registration will only enable the first survey, which is pretty basic and unremarkable. If you'd like to check out some of the more sophisticated ones, shoot me an email at sngardner {AT: wisc.edu with [HN] in the subject and I'll set you up with a test account.
Thanks for any feedback you can give us, and feel free to email me directly at sngardner {AT: wisc.edu if you have any technical questions / bug reports.