Red Hat Certified Engineer
Linux vendor and consultant Red Hat, offer dedicate training and testing for their flavour of Linux. It is based around their commercial Enterprise Linux product family. The training can be purchased directly from RedHat or from resellers - training offered by RedHat themselves (at Guildford) and IBM (London and other places) in the UK. Along with the main Linux track, they also offer a ranger of other allied technologies.
There are a number of courses that make up the couse work, starting with one designed for people tottaly new to Linux, through a one week "cram" course and exam. The main tiers are:
RedHat Certified Technican (RHCT), basic introductory course covering installation and configuration of a workstation.
RedHat Certified Enginnner (RHCE), the main level, covering all the content of the RHCT, plus security and network administration.
RedHat Certified Architect (RHCA), new, covers all preceeding levels, and is designed for large scale enterprise implementations.
For better or worse, the RedHat is the mostly recognised Linux training and certification, but does have a reputation for quality and it's usefulness.