The second sort of fundamental positional measurement of stars is that of proper motion. Proper motion is the angular speed at which a star moves across the sky. It is expressed in units of arcseconds/year, or sometimes milliarcseconds/year. If one knows the distance to a star and its proper motion, one can calculate the speed it moves through space (actually only the motion perpendicular to the line of sight). The formula for this is
where V is the speed, 
is the proper motion, and d is the distance to the star.
Think about why this would be the case. Hipparchos has measured proper motions for
stars as well, and has an impressive list of the ``fastest movers'' among the stars
Fast Movers in Outer Space. The stars with the highest space velocities are moving
at several hundred kilometers per second.