We have set up mirmon to monitor the status of our mirrors.
http://mirror-status.centos.org
Please check on the status shown for your miror as there are a few that are very out of date , and a few uncontactable.
Any mirrors not listed are flagged as down in our database. Please advise if they are back up.
This data will shortly feed into the mirror list on our website, and we will be setting up a system to email admins when there mirror is bad.
Mirmon only checks the timestamp on the mirror , but does not check mirror content, so is only a rough guide, sufficient to tell whether mirrors are bad, but in effect not whether they are good ...
Our mirrorlist system checks the validity of the repodata.xml file for each repo by comparing it against the master and only offering those that match, similarily our iso redirect checks the file details against those on the master server so both check that the mirrors are good.
Cheers
Lance