LabHEART is a very user-friendly interactive computer model of integrated Cardiac Myocyte ion channel and Ca transport. It is useful for both students and researchers to understand the cardiac action potential, ion channel properties and Ca transients.
MaxChelator is an easy to use program to calculate complex ionic solutions (e.g. using Ca-EGTA-Mg-ATP etc). That is, if you need to make a solution with a specific free [Ca] and [Mg] and include Ca buffers like EGTA, EDTA, BAPTA... this will tell you how much total Ca, EGTA... to use to achieve it.
The Shannon-Bers Model is an integrated mathematical model of cardiac excitation-contraction coupling, focusing on detailed Ca handling with four compartments of junctional cleft, subsarcolemmal space, cytosolic bulk, and sarcoplasmic reticulum.