FUD Zilla has some info about a 45nm Socket AM2+ processor from AMD that is codenamed Ridgeback:
Our well informed sources have confirmed that AMD is working on a desktop version of the Shanghai 45 nanometre CPU. This CPU is planned for mid 2008 and it supports socket AM2+.
Marchitecture wise it is the same core as Shanghai, but it will support AMD's AM2+ socket. Shanghai and the Phenom FX version of Shanghai will work on socket 1207+ while this new core will work on the much cheaper AM2+ platform.