Fglrx

AMD Catalyst (fglrx) is the closed source binary driver for AMD/ATI graphic cards. It was mainly written by ATI to support their FireGL cards on Linux workstations and later AMD continued work as an alternative to their open source effort on the Radeon driver.

Installation
Support for older cards has been dropped in the binary driver, you might want to check if the card is supported: AMD HCL AMD provides a legacy driver version for unsupported cards or use the Radeon driver.

Kernel
Any DRM and Radeon related code should be disabled in the kernel or it might interfere with the closed driver.

USE Flags
USE flags for

Initial setup
This will generate an initial xorg.conf which uses the fglrx driver:

If this command fails without error, copy the file to the default location

Set the opengl driver to use fglrx

External resources

 * unsupported cards and legacy driver download
 * community wiki article