RelaxIS is a stand-alone impedance analysis software.

It offers extensive capabilities in handling impedance data, plotting it in various different representations (Nyquist, Bode, custom) and transfer functions and fitting the spectra to equivalent circuits or physical models (including Autofitting capability).
RelaxIS also allows further evaluation of the fit results, e.g. creating custom plots of fit results vs. metadata (e.g. temperature) or by performing built-in Arrhenius- and VFT fits.
The included Circuit Simulator is also extremely helpful in teaching impedance spectroscopy by giving the ability to free define, plot and change simulated data of equivalent circuits or other models.