  Significant progress has been made during the last 10 years toward resolving
the debate over the expansion rate of the Universe. The current value of the
Hubble parameter, Ho, is now arguably known with an accuracy of 10%, largely
due to the tremendous increase in the number of galaxies in which Cepheid
variable stars have been discovered. Increasingly accurate secondary distance
indicators, many calibrated using Cepheids, now provide largely concordant
measurements of Ho well out into the Hubble flow, and deviations from the
smooth Hubble flow allow us to better measure the dynamical structure of the
local Universe. The change in the Hubble parameter with redshift provided the
first direct evidence for acceleration and "dark energy" in the Universe.
Extragalactic distance measurements are central to determining the size, age,
composition, and fate of the Universe. We discuss remaining systematic
uncertainties, particularly related to the Cepheid calibration, and identify
where improvements are likely to be made in the next few years.
