We report on a novel micromechanical photonic integrated circuits (PIC) for integrating free-space optical systems on a chip. Using polysilicon surface-micromachining technique, micro-optical elements, three-dimensional optomechanical structures, and microactuators are monolithically integrated on silicon substrate. We will discuss the basic building blocks of the micromechanical PIC, including XYZ micropositioners, 2-axis tilting micromirrors, scanning microlenses, and their integration with vertical cavity surface-emitting lasers. We will also discuss their applications in reconfigurable optical interconnect and active alignment in parallel free-space optical interconnect systems.