Homebrew

From PostgreSQL wiki

Homebrew is a package manager for Mac OS X that builds software from its source code. It includes a version of PostgreSQL packaged by what it refers to as a formula. This type of installation might be preferred by people who are comfortable using the command line to install programs, such as software developers.

Notes on Homebrew:

• Install PostgreSQL 9 on OS X (2010-11-25) - Easy install using Homebrew package manager.
• Brew Install Postgresql on OS X Lion - Resolving conflicts with the built-in PostgreSQL libraries shipping with OS X 10.7 'Lion'
• Discussion comparing Homebrew and EDB OS X installers
• petere/postgresql tap for installing multiple PostgreSQL versions in parallel