Sometimes, packages you never actually use get installed as dependency by yum (or even during initial installation by anaconda). package-cleanup is a great tool that helps you find packages not required by other packages. It it part of the yum-utils package which can easily be pulled with yum:

# yum install yum-utils

1. Find and review “unused” packages

You can find packages not required by other packages with

# package-cleanup --leaves

These packages could be candidates for removal, but check to see whether you use them directly or if they are used by applications not backed by rpm packages.

2. Find and review “lost” packages

You can find orphaned packages (i.e. packages not in the repositories anymore) with

# package-cleanup --orphans

This will also show packages which have been partially uninstalled but where the “%postun” script failed.

See also package-cleanup manpage