The online docs from Red Hat were a HUGE study aid for me:
http://www.redhat.com/docs/manuals/enterprise/
I downloaded the System Administration Guide, the Intro to System Administration book, and the Reference Guide.
I also printed out the course outline for RH133 (the RHCT class) and went over it using the above books. Every topic was covered. This really prepared me for the class. I passed the RHCT with little or no trouble, and later on, the RHCE.
I hope it helps for you!!
Good Luck!