accessiBe - Making websites accessible to people with disabilities
Dr. Link Check - Broken link checker with malware and parked domain detection
Sim Daltonism - From the perspective of a color blind person, some colors are impossible to distinguish.
BrokenLinkCheck - Free Broken Link Checker / Online Dead Link Checking Tool - find bad hyperlinks
Coblis - If you are not suffering from a color vision deficiency it is very hard to imagine how it looks...
DRKSpiderJava - DRKSpider is an open source website crawler (sitemap generator) and link checker. Features: