Listed below are the tools we’ve been using when we are building stuff for the web, hope you may find it useful and helpful for you as well:

REM Calculator CSS – Tool to calculate the rem sizes
dopethemes.com/rem-calculator-css

Composer – Dependency Manager for PHP
getcomposer.org

Node.js – Package ecosystem of open source libraries
nodejs.org

PHPUnit – Testing framework for PHP
phpunit.de

Vagrant – Virtual machine environments for workflow and automation
www.vagrantup.com