accessiBe - Making websites accessible to people with disabilities
Colour Contrast Analyser - TPGi's ADA Color Contrast Checker checks for helps determine the accessibility the contrast ratio of two colors for WCAG AA and AAA.
Page Speaker - Modern web accessibility tools for agencies & webmasters
Who Can Use - WhoCanUse is a tool that brings attention and understanding to how color contrast can affect different people with visual impairments.
tota11y - An accessibility visualization toolkit from Khan Academy
Kontrast - Check and adjust web element contrast in real time.