A while ago there was an update to the YUM package management system for CentOS. It’s quick and painless and if youre NOT behind a proxy it’s actually recommended by the devs as well.
To install it simply type:
# yum install yum-plugin-fastestmirror
And you’re done!
Now everytime you run a yum update yum will automatically select the fastest mirror for your server and download the files.
A note though: If you find that it fails frequently after a popular security patch or update has been released, you may need to type yum update several times before it actually gets through. It hasn’t happened me to much though.