With even early stage products getting thousands, if not millions, of users in lightning fast speed compared to their alumni counterparts having a strong infrastructure for your high availability systems is an issue now for companies of all sizes. Most use great and proven open source technologies like Chef or Puppet. However, there are other great tools when it comes to helping your development operations and/or infrastructure hold up the best it can.
1) Test Kitchen (http://kitchen.ci/) :Test Kitchen is a test harness tool to execute your configured code on one or more platforms in isolation. A driver plugin architecture is used which lets you run your code on various cloud providers and virtualization technologies such as Amazon EC2, Blue Box, CloudStack, Digital Ocean,Rackspace, OpenStack, Vagrant, Docker, LXC containers, and more. Many testing frameworks are already supported out of the box including Bats, shUnit2, RSpec, Serverspec, with others being created weekly.
2) Vagrant (https://www.vagrantup.com/) is a cookbook that allows you to create and configure lightweight, reproducible, and portable environments.
3) Jenkins (http://jenkins-ci.org/) is certainly not new to the scene but is a great and often overlooked extensible open source continue integration server.
4) Foodcritic (http://acrmp.github.io/foodcritic/) is a self described "lint tool" for your Chef cookbooks.
Question of the day: What is the core difference between a DevOps Engineer and a Site Reliability Engineer?