FEniCS is an automated finite element library used to solve equations used in modeling, featuring a domain-specific language and automated code generation. Users input a problem that looks very much like mathematical notation; FEniCS then translates that into computer code.
Julia is a fast and user-friendly programming language for high-performance scientific computing.
Stan is a platform for Bayesian modeling, inference, and visualization on the frontiers of applied statistics.
IPython is an enhanced interactive Python environment aimed at maximizing productivity in workflows that combine data, computation and exploratory programming. It gave rise to the larger, cross-language Project Jupyter, and it continues to provide the default Python environment for the Jupyter platform.