Integrating an SMT solver in a certified environment such as an LF-style proof assistant requires the solver to output proofs. Unfortunately, those proofs may be quite large, and the overhead of rechecking the proof may account for a significant fraction of the proof time. In this paper we explore techniques for reducing the sizes of propositional proofs, which are at the core of SMT proofs. Our techniques are justified in an algebra of resolution and rely on a graph-theoretical representation of proofs that allows us to detect the potential for reordering and combining resolution inferences.