The MolSpin software package is a virtual spin dynamics laboratory that allows exploration of any spin system or any process involving spins.
It is designed to be as general as possible, and with a great emphasis on extensibility making it easy to implement new algorithms when the standard features does not suffice - and extending MolSpin is much easier than writing a new script in e.g. Matlab. Also note that in contrast to other spin dynamics software packages, MolSpin is not limited to specific calculation types, such as solving the Liouville-von Neumann equation, but can also support completely different tasks such as semi-classical simulations or simulate a quantum computer.
Another notable feature of MolSpin is the use of trajectories for all input parameters, which allows, for example, to specify complex time-dependences of parameters such as spin-spin interaction tensors or external magnetic fields. The use of trajectories was originally implemented to allow a more direct coupling between molecular dynamics simulations and the spin dynamics than provided by spin relaxation theory, hence the name Molecular Spin Dynamics or MolSpin for short.