GetBonNie is a web-based application for building, analyzing and sharing rule-based models encoded in the BioNetGen language (BNGL). Tools accessible within the GetBonNie environment include (i) an applet for drawing graphs that correspond to BNGL code, (ii) a network-generation engine for translating a set of rules into a chemical reaction network, (iii) simulation engines that implement generate-first, on-the-fly and network-free methods for simulating rule-based models, and (iv) a database for sharing models, parameter values, annotations, simulation tasks and results.