I have just completed the preliminary version of a (OpenConference <-> CK-ERP) connector. A demo of (OpenConference 2.1.1 + CK-ERP 0.29.1) is available at,http://ck-erp.org/ocs/
(please login using, username=demouser, password=demouser)
As far as I can tell, an (OpenConference + CK-ERP) installation will be most useful to educational institutes and/or conference organizers. They will be able to maintain a conference's accounting book within OpenConference's login environment.