I've successfully added transmission line elements to the Smith Chart matching web app here on RFMentor.com. These include series, shorted shunt section, and open shunt section. There's a trick you can use to have these transmission line elements use an arbitrary characteristic impedance. The elements adopt the same characteristic impedance as the chart normalization impedance (default is 50 Ohms).
An early version of the Smith Chart web app is now available to try out. There are a couple of issues that I will be working on initially, such as the frequency entry dialog box appears to be transparent for some reason. I'll also be working on the layout to try and make the various parts of the app fit better on the page. At the moment, the app is only optimized for mouse input and does not respond to touch-based dragging events (to move elements around on the chart).
Now that browsers are dropping support for the Java plug-in, it seems that the days of applets are coming to an end. Although Java applets never dominated the mainstream web experience as much as more popular Flash-based content, they did find a niche in scientific and engineering applications - which is one of the few areas where they will likely be missed.
Another application of using Python to demonstrate RF concepts comes in the form of a calculator to plot L-C series reactance. This plot shows two useful concepts: resonance and the effect of parasitic capacitance or inductance. For a capacitor, the magnitude of the series reactance decreases with increasing frequency, while the opposite is true for an inductor. For a capacitor with parasitic inductance, there will come a point where the two reactances are equal in magnitude and cancel each other out. This point is the resonant frequency of the combined circuit.