Web development - toolbox

I'll list tools I daily use for various web development tasks, please add any interesting tools, sites, scripts if you think that they are "must use" or at least "must check"

Dissimilar: this is work in progress

Back-end

API

• Mock or even build REST & SOAP APIs with getsandbox.com, free for 5K request per month, 6.8.2015 

Front-End

• lorempixel.com placeholder images for every need, 6.8.2015 

Mobile

UI Frameworks

• Ionic framework, currently most popular mobile HTML presentation framework, it lies upon AngularJS
• PolymerJS (web components to modern browsers, pre-alfa); check following presentation webcomponents revolution

Interesting blogs and posts

• The Landscape Of Front end Development Automation (slides, one of most comprehensive overviews of front-end development tools and practices)
• http://web-appz.blogspot.com/