While you're using Mac OS X Server, you should keep track of current updates and other tips and tricks that pop up as Apple updates the software. Following are some resources to keep handy:
http://train.apple.com/Information about Apple's Training courses.
http://www.apple.com/support/macosxserver/Apple's support site for Mac OS X Server.
http://www.openldap.org/The place to learn more about LDAP, which is a must when you're dealing with Mac OS X Server and many users and groups.
http://web.mit.edu/kerberos/www/krb5-1.3/krb5-1.3.1/doc/krb5-admin.htmlMIT's site about Kerberos.
http://alienraid.org/A site devoted to using Apple's Xserve RAID in non-Apple environments.
http://www.itinstruction.com/Training and education for Mac OS X and Mac OS X Server.
http://www.afp548.com/An excellent resource to find all sorts of advanced tips and tricks for dealing with various aspects of Mac OS X Server.
http://www.mac-mgrs.org/A site devoted to a listserve that focuses on managing and troubleshooting Mac OS X and Mac OS X Server. If you can't find the answer anywhere else in the world, do your homework, read the list rules, and get your answers here. This is Mac-based community support at its finest.
http://www.macenterprise.org/The Mac OS X enterprise deployment project.