Here are additional third party resources to check out:
buildingSMART International (International Alliance for Interoperability)
The international organization that emphasizes the demonstration of "... the efficiency and sustainability benefits that true interoperability can deliver and to help members and their supply chains in implementation." It is responsible for the development and management of IFC.
The U.S./North American chapter of buildingSMART, a council of the National Institute of Building Sciences (NIBS), coordinating the U.S. efforts of promoting interoperability in the real property industry.
National BIM Standard (NBIMS)
The focal point for the activities in establishing standards regarding the use of BIM methodologies and technologies in the U.S.
The U.S. General Services Administration (GSA) 3D-4D Building Information Modeling
The GSA is considered the largest landlord in the U.S. and has made extensive efforts in transforming their organization by integrating BIM methodologies and technologies into the design, construction administration, and facility management of U.S. federal properties.
AIA Building Connections
The American Institute of Architect's (AIA) "... International Clearinghouse for Interoperability Standards and Activities in the Architecture, Engineering, Construction and Real Estate industries."
IFC2x Edition 3
The online technical reference documentation for IFC 2x3.
IFC Solutions Factory
The online technical reference documentation for the use of Model View Definitions (MVDs), documenting the IFC data requirements for exchanges of BIM information between applications.