Here's a list of free tools that you can use to check your website for accessibility– Web based or downloadable.
Accessibility Valet - Site Valet
Accessibility Valet is a tool that allows you to check Web pages against either Section 508 or WGAC accessibility compliance. One URL at a time may be checked with this online tool in free mode, or unlimited use with paid subscription.
Adobe Acrobat PDF Converter - Adobe
Adobe offers this resource for converting PDF files into either HTML or plain text. The PDF file must be online and a URL given to the converter to process. Note that only text is output: graphics and other non-text elements are simply dropped.
Cynthia Says - HiSoftware
The Cynthia Says portal is a Web content accessibility validation solution. It is designed to identify errors in your content related to Section 508 standards and/or the WCAG guidelines. This free tool, meant for educational purposes, is an online test which only validates one page at a time.
TAW3 - CTIC Foundation
TAW3 is a tool for the analysis of Web sites, based on the W3C - Web Content Accessibility Guidelines. It will check one URL at a time from its Web-based mode, or offers downloadable versions for your desktop or browser.
WAVE - WebAIM
WAVE is a free Web accessibility evaluation tool provided by WebAIM. It is used to aid in the Web accessibility evaluation process. Rather than providing a complex technical report, WAVE shows the original Web page with embedded icons and indicators that reveal the accessibility information within your page.
Vischeck - Vischeck
Vischeck is a tool for showing what things look like to someone who is color blind. You can try Vischeck online by either running Vischeck on your own uploaded image files or by running running it on a Web page by feeding it a URL. You can also download the program as a Photoshop plugin to use it on your own computer.
Dreamweaver Accessibility Plugins - Adobe/Macromedia
Dreamweaver is the most popular and capable WYSIWYG Web page editor on the market today. Adobe Software offers a collection of vendor and third-party supplied plugins and add-ons that give a wide range of accessibility checking options.
Insight - Colorfield Digital Media
Colorfield Insight is a Photoshop plug-in that allows designers to predict image legibility for color deficient viewers by accurately simulating color blindness. Given that up to 10% of the male population is affected by some sort of color blindness, Web page designers should use a tool such as this to preview their pages to make sure important information is not being lost.