Apple provides training courses on Mac OS X and OS X Server. I think they're quite good, but I'm biased, because I teach them. The courses are a good way to prepare for the Apple Certified Technical Coordinator exams.

You are not required to take the courses in order to take the exams; if you already know all everything about everything, you can just go take them. But most people I know who took the exams took the courses first, including me. You also don't have to take the certification exams after taking the course, but most of my students do.

-MarkPilgrim