Follow these useful links to discover more:
News Sources
Covering advanced packaging, 2.5D/3D, interposers, heterogeneous integration, etc.
Research Groups
Non-profit organizations performing invaluable R&D
DARPA (see especially their DAHI and CHIPS programs)
IEEE Electronics Packaging Society
Standards Groups
Supplying structure and direction for the burgeoning field
Manufacturers
Providing advanced microelectronics services and licensing for customers