webhint : webhint is a linting tool that will help you with your site's accessibility, speed, security and more, by checking your code for best practices and co...
Diagnostic.css : Diagnostic.css is a stylesheet which allows the user to test for common errors in a page's markup.
Also : https://github.com/karlgroves/diagnostic.css
Skipfish : Skipfish is an active web application security reconnaissance tool. It prepares an interactive sitemap for the targeted site by carrying out a recursi...
WebScarab : WebScarab is a framework for analysing applications that communicate using the HTTP and HTTPS protocols.
Catches mail and serves it through a dream.
MailCatcher runs a super simple SMTP server which catches any message sent to it to display in a web interface.