Today there is a paper on the astro-ph archive by Dave Champion and collaborators describing some of the pulsar timing they have been doing with the Arecibo radio telescope in Puerto Rico. You will have seen this telescope if you have even watched the film Contact (where Jodie Foster goes looking for alien signals) or the James Bond film GoldenEye (where it gets destroyed at the end).
What the researchers have done is use the telescope to measure the pulse profiles of a number of pulsars. Most pulsars are weak radio sources so to accurately measure the shape of the pulse profile you need to measure many of them and add the signals together. This is useful because the shape of the pulse profile can provide information on the characteristics of the emission regions on the surface of the pulsar itself, telling us about the extreme physics involved. Using the observations they measured "drifting subpulses", features in the pulse profiles that move with time. These are thought to be caused by small patches of emission, sub-beams, on the surface of the pulsar which move in and out of our line of sight and so appear to come and go.