I just set up a new Tier 2 public mirror.  It is accessible via HTTP at http://www.vsvinc.com/centos/.
It is synchronised every six hours.  There is a 5MB limit.
The site is in Fitchburg, MA, USA.
The sponsoring organisation is V. S. V., Inc. (http://www.vsvinc.com).
The contact email is repo@vsvinc.com.