  Accurate measurement of pulsar distances via astrometry using very long
baseline interferometry enables the improvement of Galactic electron density
distribution models, improving distance estimates for the vast majority of
pulsars for which parallax measurements are unavailable. However, pulsars at
southern declinations have been under-represented in previous interferometric
astrometry campaigns. In order to redress this imbalance, we have conducted a
two-year astrometric campaign targeting eight southern pulsars with the
Australian Long Baseline Array. The program summarized in this paper has
resulted in the measurement of seven new pulsar parallaxes, with success on
objects down to a mean flux density of 0.8 mJy at 1600 MHz. Our results
highlight the substantial uncertainties that remain when utilizing free
electron density models for individual pulsar distances. Until this study, PSR
J0630-2834 was believed to convert 16% of its spin-down energy into x-rays, but
our measured parallax distance of 332 (+52 -40) pc has revised this value to
<1%. In contrast, PSR J0108-1431 was found to be almost a factor of two more
distant than previously thought, making its conversion of spin-down energy to
x-rays the most efficient known (>1%). The 8.5 second radio pulsar J2144-3933
was found to be closer than previously predicted, making its apparent 1400 MHz
radio luminosity the lowest of any known pulsar (20 microJy kpc^2). We have
examined the growing population of neutron stars with accurate parallaxes to
determine the effect of distance errors on the underlying neutron star velocity
distribution, and find that typical distance errors may be biasing the
estimated mean pulsar velocity upwards by 5%, and are likely to exaggerate the
distribution's high-velocity tail.
