Web Standards & Accessibility Testing Tools

Accessibility
The WAI has 86 different Accessibility validation tools listed at http://www.w3.org/WAI/ER/tools/Overview

Out of these, I think the Web Accessibility Inspector from Fujitsu  at http://www.fujitsu.com/global/accessibility/assistance/wi/ is the best for local testing - although it only support WCAG 1.0.


After a bit more research, I think one of the best for WCAG 2.0 is AChecker  at http://www.atutor.ca/achecker/. This is an open source Web accessibility evaluation tool that can be both used locally and via a hosted service.

Web Standards
When it comes to validating, HTML, XHTML, XML and CSS, there are a stack of tools listed at http://www.w3.org/TR/WCAG20-TECHS/G134.html. Probably the best of these is the WC3 Validator service at http://validator.w3.org/