More yum documentation: Robert G. Brown's Yum (Yellow dog Updater, Modified) HOWTO
Randolph J Tata's CDServer-HOWTO
The Linux Documentation Project, specifically the Linux Complete Backup and Recovery HOWTO at the usual places.
Jeremy Impson's Build a Virtual CD-ROM Jukebox
How do I get all the latest stuff for Fedora using apt? It includes a section on yum.
Robert P. J. Day's yum tutorial
Shekhar (or Shon)'s "How to create yum repository" shows how to set up and automate getting updates into your local repository.
FedoraNEWS.ORG runs useful articles on Fedora in general, and on yum.
"Fedora Tracker aims to be a comprehensive but easy to use index of Fedora apt/yum repositories on the internet. You can search by repository or by package. The repository search mode will even generate apt and yum config files for you!"