For those of you lucky enough to have one flatscreen and keyboard per child, this might be especially interesting, but also if you share computers and/or just project:
Python + VPython, both free and open source projects, from python.org and vpython.org respectively, will let your students deliver moving pictures to the screen based on very few instructions involving the concepts we're supposed to be teaching (e.g. sine, cosine, radians, degrees), and in a concise computer language with job market value, so easy to prove relevance (as in "what will we use this for??").
Example: the code below is sufficient to produce a lissajous curve, with just a few lines omitted (click plaintext view in web archive interface to see original indentation):
def lissa(): # you could make a, b arguments if you want """ Lissajous curves: