Esta página permite comprobar si dos colores tienen el suficiente contraste, calculando la diferencia de brillo y color de acuerdo al algoritmo sugerido por el W3C.
WAVE is a free web accessibility evaluation tool. It is used to aid humans in the web accessibility evaluation process. WAVE shows the original web page with embedded icons and indicators that reveal the accessibility information within your page.
An analysis of popular web-based survey research tools and how well they work a variety of accessibility tests. SurveyGizmo was rated best, followed by SurveyMonkey.
W3C link checking service. Feed it your URL and some options. The output format is not exactly "user-friendly", but it is clever enough to obey robots.txt when checking links.