"Bobby is a web-based tool that analyzes web pages for their accessibility to people with disabilities." Use this to test pages that are already on the web.
If you create web page content, then download Bobby to run on your own computer.
"WebABLE! is the authoritative Web site for disability-related internet resources."
You also might want to see how your sites looks on WebTV by using the WebTV simulator to preview your pages.
Web Page Accessibility Checklist (for Federal agencies.)
"After you have evaluated this Web page using the Checklist, test it by running it with a text-only browser, such as Lynx, a public domain text browser that is available at http://lynx.browser.org."