Hi,
For a brief rundown on metalinks, try one of these:
http://torrentfreak.com/metalinker-integrating-http-ftp-and-p2p/
http://www.downloadsquad.com/2006/08/28/metalinks-integrated-bittorrent-http -and-ftp-downloads/
aria2 (metalink/bittorrent command line client) RPMs for FC 1,2,3 & RHEL 3,4 (i386 & x86_64) are available at:
http://apt.sw.be/packages/aria2/
A CentOS metalink is at http://www.metalinker.org/samples.html#isos for anyone who would like to try it out.
http://metalink.packages.ro/ which is run by one of the CentOS mirrors, could automatically generate metalinks for you like it does for OpenOffice.org.
Anthony Bryan metalink [ http://www.metalinker.org ]