Browserling – an awesome cross-browser testing service, has a collection of Web Developer Tools, which are as simple to use as possible. There are now more than 80 (!!!) tools, according to this Peteris Krumins blog post, that provide immediate help with things like converting dates and times, formats like CSV, JSON, Markdown, HTML, XML, etc, generating passwords, minimizing or prettifying HTML, CSS, JavaScript, and more.