Graphene has emerged as an interesting material for plasmonic applications in the terahertz to mid-infrared, the spectral region where its plasmonic resonance typically resides.  The coupling behavior of graphene plasmons with both molecular vibrations and other plasmons will be presented.  Plasmon energy dispersion with the number of stacked graphene layers allows for the creation of multi-mode plasmonic structures, where unconventional plasmon-plasmon hybridizations arise, resulting in an increased infrared absorption bandwidth.  Interaction of graphene plasmons with molecular vibrations results in electromagnetically induced transparency phenomena in plasmon light absorption, thereby increasing the effective infrared absorption cross section of the molecular vibrations.  As both bandwidth enhancement and detection sensitivity enhancement have practical value, potential technological implications of these results will also be discussed.