yumdownloader で、できるんですね。
downloadonly のpluginだと、インストールしたものは、持って来れなかったので。。

[guutara rpm]# sudo yum -y install yum-utils
Loaded plugins: downloadonly, fastestmirror, priorities
Loading mirror speeds from cached hostfile
 * rpmforge: fr2.rpmfind.net
34 packages excluded due to repository priority protections
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package yum-utils.noarch 0:1.1.16-14.el5.centos.1 set to be updated
--> Finished Dependency Resolution

Dependencies Resolved

 Package                             Arch                             Version                                           Repository                      Size
 yum-utils                           noarch                           1.1.16-14.el5.centos.1                            base                            69 k

Transaction Summary
Install       1 Package(s)
Upgrade       0 Package(s)

Total download size: 69 k
Downloading Packages:
yum-utils-1.1.16-14.el5.centos.1.noarch.rpm                                                                                           |  69 kB     00:00     
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing     : yum-utils                                                                                                                             1/1 

  yum-utils.noarch 0:1.1.16-14.el5.centos.1                                                                                                                  


[guutara rpm]# yumdownloader 
Loaded plugins: fastestmirror, priorities
usage: "usage: yumdownloader [options] package1 [package2] [package..]

  --destdir=DESTDIR     destination directory (defaults to current directory)
  --urls                just list the urls it would download instead of
  --resolve             resolve dependencies and download required packages
  --source              operate on source packages
  --archlist=ARCHLIST   only download packages of certain architecture(s)
                        Priority-exclude packages based on name + arch

  Plugin Options:

  Yum Base Options:
    -h, --help          show this help message and exit
    -t, --tolerant      be tolerant of errors
    -C                  run entirely from cache, don't update cache
    -c  [config file]   config file location
    -R  [minutes]       maximum command wait time
    -d  [debug level]   debugging output level
    --showduplicates    show duplicates, in repos, in list/search commands
    -e  [error level]   error output level
    -q, --quiet         quiet operation
    -v, --verbose       verbose operation
    -y                  answer yes for all questions
    --version           show Yum version and exit
                        set install root
                        enable one or more repositories (wildcards allowed)
                        disable one or more repositories (wildcards allowed)
    -x [package], --exclude=[package]
                        exclude package(s) by name or glob
                        disable exclude from main, for a repo or for
    --obsoletes         enable obsoletes processing during updates
    --noplugins         disable Yum plugins
    --nogpgcheck        disable gpg signature checking
                        disable plugins by name
                        enable plugins by name
    --skip-broken       skip packages with depsolving problems
    --color=COLOR       control whether color is used

  yumdownloader options: