motiondesign / typo : kinetic typography
kinetic typography is the art of representing spoken word as a typographic animation
http://www.alwayswatching.org/features/
great-scenes-television-and-film-told-using-only-typography
on youtube are quite many examples too:
http://www.youtube.com/results?search_query=
kinetic+typography&search_type=
via nerdcore
