Fabian: See also #centos-mirror. I posted this information also to the mailing list to retain a paper trail of the changes.
I noticed that some mirrors have changed their ftp and rsync URLs. Here are the apparent new ones:
old: ftp://mirror.nus.edu.sg/pub/centos/ new: ftp://mirror.nus.edu.sg/html/centos/
old: ftp://mirror.inode.at/data/centos/ new: ftp://mirror.inode.at/centos/
old: ftp://centos.mirror.transip.nl/Centos/ new: ftp://centos.mirror.transip.nl/centos/
old: ftp://ftp.mirror.ukhost4u.com/ new: ftp://ftp.mirror.ukhost4u.com/centos/
old: ftp://centos.mirror.crucial.com.au/ new: ftp://centos.mirror.crucial.com.au/centos/
old: ftp://mirrors.ucr.ac.cr/pub/centos/ new: ftp://mirrors.ucr.ac.cr/centos/
old: rsync://ftp.byfly.by/pub/CentOS/ new: rsync://ftp.byfly.by/CentOS/
old: rsync://mirror.crazynetwork.it/centos/ new: rsync://mirror.crazynetwork.it/CentOS/
old: rsync://ftp.pbone.net/pub/centos/ new: rsync://ftp.pbone.net/centos/
old: rsync://mirrors-ru.go-parts.com/centos/ new: rsync://mirrors-ru.go-parts.com/mirrors/centos/
old: rsync://centos.mirror.lstn.net/ new: rsync://centos.mirror.lstn.net/centos/
Sadly this does not mean that all the other ftp and rsync links would work. There were numerous "connection refused", "login incorrect", "connection timed out", "permission denied" etc errors, but I guess I'll save them for some other posting.