Download Windows Self Shot! (VistaCam.gadget) from
here (resource no longer available) for Windows Vista Sidebar. Once installed, Windows Self Shot! gadget will stream live feed video from the webcam or camera installed on your computer in a gadget window located in sidebar. You can actually move the streaming video window all over your desktop once installed.
Other than looking into yourself, you can also place your webcam in any corner of your house (as long as you have a long USB cable) for monitoring the corner, such as watching your baby sleeping in the room and etc.