Information about the IFC format can be found at the web-pages provided by buildingSMART Model Support Group (MSG) at http://msg.buildingsmart.com. MSG is handling maintnance, extensions and releases of the IFC format.
buildingSMART also provides a Implementers Support Group (ISG) for software companies implementing support for the buildingSMART standards. In addition to regular meetings and certification of compliant software, ISG is also the place where implementers discuss and make "implementers agreements" for how to solve various issues related to implementation. More information can be found here.