W3C Markup Validation Service - Validates HTML markup of web pages, one at a time.
Life Calendar - Your life in weeks
HTML Validator - HTML Validator is a Mozilla extension that adds HTML validation inside Firefox and Mozilla.
Kin Calendar - The simple and connected calendar
Rocket Validator - Site-wide Accessibility and HTML validation made easy. With a single click, Rocket Validator will check thousands of web pages on your site for Accessibility and HTML conformance, producing a detailed, actionable report on seconds.
WeCroak - An app to remind you of death