Are there any computer vision algorithms specifically targeting depth images?
My favourite 2.5D/3D feature descriptor for registration and recognition is the spin image (original paper + more details in Ph.D. thesis and software available from CMU).

Other recent advances (all searchable on-line for suitable algorithims) include: 3D-Sift, Fast Point Feature Histogram,  Normal Aligned Radial Features (NARF), Depth Kernel Descriptors. Older methods simply used surface properties such as curvature and edges to identify region patches.

Which is best? Depends on what you want to find, viewpoint invariance, additional clutter, etc.