ISO 9001:2000, CMMI, and Six Sigma share many similar characteristics.
The programs can be implemented independently or in tandem with one another.
ISO 9001:2000 is a generic quality standard that can be implemented in any production environment.
ISO 9001:2000 may be best used in organizations where the quality system required crosses many different types of functional areas.
The Capability Maturity Model Integration is a process improvement model specifically designed for use in technology development environments.
CMMI may be best used in IT shops that are charged with systems and software development.
Six Sigma is a process improvement approach based in statistical analyses and geared toward shaping process to reflect the Voice of the Customer.
Six Sigma may be best used in environments that are transaction intensive: those in which many similar actions are run through a set of stable processes.