A decade ago, two teams studying distant type Ia supernovae discovered that the 
expansion of the Universe is speeding up. Since then, supernova surveys 
from the ground and from space have brought major improvements 
in the quality and quantity of SN Ia data, confirming the discovery of 
cosmic acceleration. This talk will focus on the first cosmological results from the Sloan 
Digital Sky Survey-II Supernova Survey, which operated for 9 months in 
2005-7, discovering and measuring light curves and spectra for over 500 SNe Ia.  
I will also discuss the observational challenges to determining supernova 
distances for cosmology and how those challenges are being addressed. These results inform the 
prospects for using supernovae to obtain improved cosmology measurements 
from planned and proposed surveys in the future.