  Combined with X-ray imaging and spectral data, observations of the
Sunyaev-Zel'dovich effect (SZE) can be used to determine direct distances to
galaxy clusters. These distances are independent of the extragalactic distance
ladder and do not rely on clusters being standard candles or rulers.
Observations of the SZE have progressed from upper limits to high
signal-to-noise ratio detections and imaging of the SZE. SZE/X-ray determined
distances to galaxy clusters are beginning to trace out the theoretical
angular-diameter distance relation. The current ensemble of 41 SZE/X-ray
distances to galaxy clusters imply a Hubble constant of H_0~ 61 +/- 3 +/- 18 km
s-1 Mpc-1, where the uncertainties are statistical followed by systematic at
68% confidence. With a sample of high-redshift galaxy clusters, SZE/X-ray
distances can be used to measure the geometry of the Universe.
