While looking for something completely different, I found a nice computer program that allows you to play around with stellar spectra. It consists of two parts – in the first one you have to classify 24 spectra, whereas in the second part you can take your own spectra using a simulated telescope (three in fact, with apertures of 0.4, 1.0 and 4.0 meters).
The software was designed as part of the Project CLEA, and can be downloaded here. Though I think that the first part is a bit too easy, the second part (where you take your own spectra using the simulated telescope) is pretty interesting, especially for students who do not have access to a real telescope.
Just as a note… A small problem might arise if you are working under Linux, because the program runs exclusively under Windows. 
