iStopMotion

iStopMotion allows you to create an animation movie by means of separately capturing the frames it's composed of. The only necessary tool to produce the sequence is a webcam.

It supports characteristics like the chroma (chroma key) that allows you to place the figures on a virtual background generated by the computer, or tracing paper that lets you see the former frame captured on the image in real time showed by the webcam.

iStopMotion also lets you record frames continuously, you only have to indicate the number of seconds or squares you want to capture, and it can also add a frame to the sequence.

FrameByFrame is a free alternative to iStopMotion that, even if it doesn't have so many functions, can also be used to produce a short animation movie.