Despite intense observational and theoretical study, the progenitors of Type Ia supernovae remain uncertain. Recent observations are challenging the commonly held view that the exploding star always has a mass near the Chandrasekhar limit. I will review the different channels leading to the thermonuclear disruption of a carbon oxygen white dwarf, focusing on how these scenarios might be discriminated using observations of supernova spectra, light curves, and polarization. I will describe some theoretical predictions which may be useful in testing both the single degenerate and double white dwarf merger scenarios, and offer some model comparisons to recent observations of so-called "super-Chandrasekhar mass" events. I will also present predictions for some more exotic channels, including direct white dwarf collisions and white dwarf tidal disruption by a black hole.