RStan, the R interface to Stan
PyStan, the Python interface to Stan
The Stan Math Library is a C++ template library for automatic differentiation of any order using forward, reverse, and mixed modes. It includes a range of built-in functions for probabilistic modeling, linear algebra, and equation solving.
bayesplot R package for plotting Bayesian models
rstanarm R package for Bayesian applied regression modeling
shinystan R package and ShinyStan GUI
Emacs mode for Stan.