Nibbler - Free tool for testing how good your website is, and what you can do to improve it. Check accessibility, SEO, social media, compliance and more.
Jason - Infinitely hackable mobile client
tota11y - An accessibility visualization toolkit from Khan Academy
Pennywise - Cross-platform application to open any website or media in a floating window
Accessible Metrics - Digital Governance
Visio - Simplify and communicate complex information using data-linked diagrams.