Every time I learn a new programming language, the first thing I write is a program to generate a picture of the Mandelbrot Set. Since graphics output is usually quite involved, this often comes down to outputing some ASCII art instead of a real picture. I've probably written them in about a dozen languages now. So far the most interesting (in terms of the language itself) have been in Maude and UserRPL. Also on the list are C, C++ (Unix and Mac versions), Java (applets and applications), Mathematica, Python, Ruby, and more. I probably still have source lying around for all of them, but it will be a while before I get them all up here.