It's a bit pricey, but the LERG by Telecordia is the best implementation of
rate center homing. It pretty much has everything you need to use in a
carrier-class enviroment. However, unless you have CLEC status you are tied
into the local ILEC's rate centers.
http://www.bellatlantic.net/cgi-bin/npa-nxx/
Show's look exchanges for the Bell Atlantic area... I'm sure other RBOC's
have these as well.
Cheers
-Scott