We review recent advances in heterogeneous silicon photonic integration technology and components and describe progress in silicon photonic integrated circuits. Techniques for laser integration and the impact of active silicon photonic integrated circuits could have on interconnects, telecommunications and silicon electronics are reviewed. A variety of materials are being heterogeneously integrated, including arsenides for short wavelength lasers, phosphides for infrared lasers, QCLs for long wavelengths, LiNbO₃ and GaAs for nonlinear applications and YIG for isolators and circulators.