Pharo provides an excellent way to combat complexity in software development. With its fast feedback with instantaneous compilation of the currently edited method, its objects all the way from compiler to the run-time stack, and tools designed to be customizable by the individual developer, it supports programming your way out of a mess again. It has excellent refactoring tools and makes it easy to build domain specific languages. It values innovation and effectiveness over run-time efficiency.
Go to http://pharo.org/download and select a fitting download and run it.
There are a lot of different ways to install Pharo. Pharo itself consists of a vm and an image. In addition it needs its sources and plugins, and has some dependencies: