Vacuum energy density
Since the discovery, through Type Ia supernovae, that the expansion of the universe is accelerating and dominated by something like a vacuum energy density, this and other methods have added strong confirmation (supernova data: R Knop et al. 2003; CMB: D Spergel et al. 2003; clusters: S Allen et al. 2002). Today the picture is of a spatially flat universe consisting of only 30% dark matter and baryons, while 70% acts like an accelerating cosmological constant or dark energy.