I am a web designer that has needed to start getting into accessibility and usability and I was introduced to a great tool - LIFT for Dreamweaver. The company is called UsableNet and they launched about 6 months ago. Check out the website - www.usablenet.com or they'll even give you a free demonstration - www.usablenet.com/frontend/demoform.jsp

Hopefully it will prove to be as useful for you as it has been for me.