Photonic crystal based nanophotonic devices have been studied for various applications. One important type of devices are optical add-drop multiplexers (OADMs) that consist of photonic crystal cavities and waveguides. We show some novel device architectures and concepts to achieve better performance for such devices and discuss the non-vanishing backscattering issue. We fabricate high-quality photonic crystal waveguides on silicon-on-insulator substrates toward the ultimate goal of implementing the proposed OADM. Low optical loss, slow group velocity, and high dispersion are demonstrated in the fabricated waveguides, which is of interest to slow photon generation and optical delay line applications as well.