I am the cofounder and now the primary developer of the Union SN Ia compilations. Please see http://www.supernova.lbl.gov/Union for more information.
The key Union compilation papers are:
Union3.1: Self-consistent Measurements of Host Galaxy Properties for 2000 Type Ia Supernovae
Union through UNITY: Cosmology with 2000 SNe Using a Unified Bayesian Framework
Improved Cosmological Constraints from New, Old, and Combined Supernova Data Sets