I'm running my local development environment off of my MacBook Pro.

It consists of:

* Built in Apache/PHP, both configured how I like it

* MySQL installed via the DMG download from mysql.com

* Postgres installed via DMG download

* Redis, MongoDB, Node installed via Homebrew

* Git installed via Homebrew

* Ruby 1.8.7, 1.9.2, 1.9.3 installed and managed by RVM

* Rails and other gems installed and managed by RubyGems

* IE7, IE8, IE9 virtual machines installed via https://github.com/xdissent/ievms/