The capabilities of the SpiTanIII capacitor software from AVX Corp. have been expanded in the new Version 1.1, which now includes an S-parameter library complete with s2p files. The SpiTanIII software allows a user to select a tantalum or niobium oxide capacitor by various parameters, including capacitance, case size, or voltage rating.
The software displays a wide range of basic parameters for a selected capacitor, such as frequency characteristics of capacitance, effective series resistance (ESR), and impedance. It can be downloaded from AVX's website here, while the S-parameter library is available here.