http://dag.wieers.com/rpm/FAQ.php#B2
yum whatprovides mod_access.so
http://dag.wieers.com/rpm/packages/
http://wiki.centos.org/Repositories
For your printer see: http://openprinting.org/show_printer.cgi?recnum=Canon-iP4000
(check the FC6 Extras repo for rpm packages)
http://mirror.centos.org/centos/
http://mirrorlist.centos.org/
www.silfreed.net/download/repo/redhat/
http://www.idevelopment.info/data/Oracle/DBA_scripts/common.zip