Recently I introduced Webel, a Python cheminformatics module that runs entirely on web services. One of the advantages of such a module is that it can be used in places where it is difficult to install a traditional cheminformatics toolkit. Like in your browser.
It turns out that Silverlight ("Microsoft's Flash") provides a Python interpreter that runs in your browser. Using this, Michael Foord (of IronPython in Action) has developed an interactive Python interpreter which you can use at trypython.org. It consists of two windows, one with a Python tutorial and the other with a Python prompt so that you can work through the tutorial.
After some little work, I present Try Python...with Cheminformatics. This adds Webel as well as a short tutorial that introduces many of its features. With a few more tutorials that cover SMILES, InChI and so on in more detail, this could be useful for teaching purposes as well as bridging the gap to having students develop their own Python scripts that use the CDK, OpenBabel or the RDKit.
Here is the obligatory screenshot (click for a larger version):