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/postgresqltap for installing multiple PostgreSQL versions in parallel