Evolutionary conserved members of the Ras superfamily of small GTP-binding proteins function as binary molecular switches to control diverse biological processes. In the context of cellular signaling, these include functions in exocytic and endocytic trafficking, as well as roles in signal relay downstream of various cell surface receptors. We previously reviewed roles played by the large family of GTPase, activating proteins in these processes. In this companion review, we highlight recent findings relating to the regulation of another major class of Ras superfamily regulatory proteins, the guanine nucleotide exchange factors.