A new empirical formulae is given for estimating the masses of black holes in AGNs from the H beta velocity dispersion and the continuum luminosity at 5100 Angstroms. It is calibrated to reverberation-mapping and stellar-dynamical estimates of black hole masses. The resulting mass estimates are as accurate as reverberation-mapping and stellar-dynamical estimates. The new mass estimates show that there is very little scatter in the M_{bh} - L_{bulge} relationship for high-luminosity galaxies, and that the scatter increases substantially in lower-mass galaxies. Comment: In press in "Co-Evolution of Central Black Holes and Galaxies", IAU Symposium Proceedings No. 267, eds. B. M. Peterson, R. S. Somerville, & T. Storchi-Bergmann. Cambridge University Press, 2010. 1 figure