New top story on Hacker News: Ask HN: Best way to test accessibility of a website?

Ask HN: Best way to test accessibility of a website?
72 by pcmaffey | 28 comments on Hacker News.
Is there a bot/crawler akin to Google's Webmaster Tools that will test, score, and identify accessibility issues on a website? If not, what are some best practices people use to maintain accessibility? Does anyone write tests for this functionality? Would love to learn more, top resources, checklists people use, etc.