Certification - Apple Certified System Administrator (ACSA)

You can get a lot of info here:

http://training.apple.com/#certification

You can buy all of your books online, just search Amazon for Apple Training Series.

You can go to the classes but if you are working in the profession and have the books, you can do all the lessons and tests on your own. It is designed to be progressive so start with the basic certification and work toward ACSA.

Keep in mind, you may want to examine your options here. The time and cost to achieve the certifications may not pay off in the long run.

Look no further than the boys at AFP 548, Xsanity, Mac OS X Hints, this forum, Apple's mailing lists (although OS X Server can get a little dicey), Mac Enterprise, and your best friend Google. There are a lot of good resources out there. But I can say, the best resource is your experiences and your willingness to break stuff.

Get some spare hardware, build it, break it, build it again. With the Mini and Mini server, you can set up a 4 user test environment for less than $5000. This allows you to try nearly everything and anything (outside of Xsan). And you are not looking for high class performance, just equipment that is out of band. A mini server ($1000) + 4 minis @ $700 each ($2800) + Parallels + Windows Server. You can do AD and OD binding tests, home folders, network home folders, MCX testing, Podcast Producer testing, NetHomes, NetBoot, JAMF, SW Update, and so much more. When you look at the cost of one class, this hardware purchase pays so many more dividends.

Hope that helps.