http://www.redhat.com/docs/manuals/enterprise/ is a documentation page I always return to when I manage Redhat Enterprise Linux systems.
Redhat has put a lot of effort in their documentation and even allow you to download them as PDF documents.
The documentation below is for RHEL5.2
|Deployment Guide||May 21, 2008|
|Installation Guide||May 21, 2008|
|Virtualization Guide||May 21, 2008|
|Cluster Suite Overview||May 21, 2008|
|Cluster Administration||May 21, 2008|
|LVM Administrator’s Guide||May 21, 2008|
|Global File System||May 21, 2008|
|Using GNBD with GFS||May 21, 2008|
|Linux Virtual Server Administration||May 21, 2008|
|Using Device-Mapper Multipath||May 21, 2008|
|Tuning and Optimizing Red Hat Enterprise Linux for Oracle 9i and 10g Databases||Nov 2007|
|Online Storage Reconfiguration Guide (Beta)||July 2, 2008|
These documents is a great resource if you plan to become a RHCT or RHCE.