I will describe the search for ultra-low-frequency gravitational waves through observations of millisecond pulsars. My talk will provide a general overview, but I will also describe the status and recent results from the Parkes Pulsar Timing Array project in detail. As well as searching for the gravitational waves we use our data sets to study (1) the pulsars, (2) the interstellar medium, (3) the Solar wind, (4) magnetic fields in the galaxy, (5) developing pulsar time standard and (6) to determine the masses of planets in our solar system. The data sets can also be used for outreach activities and demonstrating reproducible pipelines. I will conclude by describing the future of pulsar timing array projects and how new observations from India, China and South Africa will all contribute.