Linux Professional Institute - Certification
The LPI is an open vendor neutral institute offering exams and certification worldwide. They do not offer training directly, rather a syllabus, and exams via partner organisations. It is up to the candidate to obtain their own training via any third party, and then sit the exams independently. Several training companies offer courses tailored for the LPIC exams, and there are a wide number of book and web sites that provide teaching and self help guides.
There are two exams for the level I certification (introductory), 101 and 102, and two exams for the level II certification (intermediate), 201 and 202. The third level exams and sylabus are in preparation at the moment - and are near completion. At the moment the exmas require both RPM and DEB package managment - this is a change from the previous arrangment of being able to take only one package system
You have to have passed LPI Level I certification before you can take Level II exams.
IBM's developerWorks LPI Series - a free set of downloadable PDFs and web pages
O'Reilly's LPI Linux Certification in a Nutshell 2nd Edition - Covers levels 1 and 2, new in 2006
Que's ExamCram2 LPIC I Exam Cram 2: LPIC Exams 101 and 102 - Covers level 1, includes full book on PDF and examware practice tests for Linux and Windows on the included CD
Paul Sheer's LINUX: Rute User's Tutorial and Exposition - a little old but the fundamentals don't change, and it's freely avaialble as PDF or HTML. Not specific to LPIC, but a useful read. Some distros include it as an installable package.