| Timing observations of radio pulsars have long been known to yield a wealth of information for a wide variety of applications. In this thesis, we describe an assortment of results obtained using this powerful technique.; We have made timing observations of 106 southern-hemisphere pulsars at the 64-m radio telescope at Parkes, New South Wales. These observations were motivated by the launch of NASA's Compton Gamma Ray Observatory, and have resulted in improved parameters for most sources and the discovery of two new gamma-ray emitting pulsars.; Serendipitously discovered in the Parkes data is the unusual binary pulsar PSR J0045-7314, the only known pulsar in the Small Magellanic Cloud. We show that the pulsar is in orbit around a {dollar}sim{dollar}10M{dollar}sb{lcub}odot{rcub}{dollar} main-sequence B star, and that the absence of eclipses and variations in the observed dispersion of the radio signal at periastron imply the companion has a surprisingly tenuous wind.; We also describe Parkes timing observations of four young pulsars, and draw conclusions about their possible associations with nearby supernova remnants. We find two of the associations to be compelling, one plausible, and one doubtful. Our timing data confirm that young pulsars have frequent period discontinuities known as "glitches," and we obtain a new confirmation of the fundamental equation of neutron star spin-down.; Finally, we describe long-term, high-precision timing observations of two millisecond pulsars using the 305-m telescope at Arecibo. We use the data for a variety of applications including cosmology, general relativity, high-precision astrometry, physics of the interstellar medium, and time-keeping metrology. For the first time, we compare the timing data for the two millisecond pulsars, and suggest that the most straight-forward explanation for the low-frequency, unmodeled signal in the PSR B1937+21 residuals is that it is intrinsic to the pulsar itself. |
