Face detection is included in FaceTrack package. It uses powerful techniques to find faces and facial features in still images in form of a well-documented Software Development Kit.
visage|SDK identifies faces and facial features in facial images containing one or more human faces. Standard image formats are supported for input images. For each detected face it returns the 2D and 3D head pose, 2D and 3D coordinates of facial feature points (chin tip, nose tip, lip corners etc.), and a wealth of other information.