Heh. I can't write one myself, but take a look at the Polyglot page for a list of for than a dozen polyglot programs (including one by BooK). The ultimate one, IMHO, is Polyglot, a ten-year-old program that compiles and runs in six or seven languages, depending on how you count. (I haven't tested it myself!)

Edit: chipmunk 2001-07-19