The Extensible Toolkit for Advanced Sampling and AnalYsis (ExTASY) is a lightweight software toolkit that supports ensemble-based simulations and their seamless integration with dynamic analysis capabilities and ultra-large time step integration methods. ExTASY enables fast sampling of the conformational dynamics of stable proteins, a prerequisite for the accurate prediction of thermodynamic parameters and biological functions. It also allows tackling systems like intrinsically disordered proteins, which can be beyond the reach of classical structural biology. ExTASY is extensible to other community software components via well-designed and standard interfaces.