use yum to download a package without installing it?

yum-downloadonly is a plugin which can be used to download packages from RHN or a configured yum repository without installing the package. Check the contents of the /etc/yum/pluginconf.d/downloadonly.conf file and make sure this plugin is enabled:

[main]
enabled=1

Please confirm package yum-downloadonly has been installed on the system for RHEL 5 or yum-plugin-downloadonly for RHEL 6. If not, this package is available on the Red Hat Network (RHN). If the system has been registered to the Red Hat Network, install the yum-downloadonly package with the following command on RHEL 5:

# yum install yum-downloadonly

and for RHEL 6:

# yum install yum-plugin-downloadonly

For example

# yum install --downloadonly vsftpd --- it will download vsftpd
Is this ok [y/N]: y Downloading Packages: (1/1):

vsftpd-2.0.5-12.el 100% |=========================| 138 kB 00:02

exiting because --downloadonly specified

Note:--The package, by default, is saved in directory /var/cache/yum/

if you want to specify your own folder then  --downloaddir with --downloadonly to yum, to specify an alternate directory to store packages:
#yum install --downloadonly --downloaddir=/tmp vsftpd