'It works on my box'. 'I don't have a day to help Dave set up his new PC'. 'I swear I had the same version installed!'
Sound familiar? It was for me too before I started using Vagrant and Ansible.
Vagrant is a tool for automating the creation of virtual machines. Of course, that's only half of the battle - once you have a machine you need to configure it. That's where Ansible comes in.
Ansible is a powerful server automation tool (think Puppet or Chef, but with a much lower learning curve), allowing you to install software and configure things as you need in a reproducible way.
By the end of this talk, everyone will be able to go home and create a Vagrant box that installs PHP, Apache2 and configures an example website with a custom VirtualHost in under 30 minutes.