Yes, I know. I have way too much time on my hands.
I wanted to practice some of what I learned from my recent compilers class (hey, I enjoy the subject), so I designed a simple LISP-like language that compiles to Whitespace. Of course, I wanted to write a small (but not trivial) application in it to test out the compiler. A sudoku solver - basically just a simple depth first search algorithm - seemed the perfect choice.
http://rapidshare.com/files/235032340/sudoku.ws
The Whitespace interpreter is here: http://compsoc.dur.ac.uk/whitespace/