This is interesting stuff, but I do wish they didn't show the solutions immediately after the question. The Prolog and Lisp versions do this better, by providing a link to the solution.
Myself and another contributor have played around with answering the 99 Prolog/Lisp/Haskell problems in Factor (<a href="http://factorcode.org/" rel="nofollow">http://factorcode.org/</a>) at <a href="http://github.com/mikejs/factor-problems" rel="nofollow">http://github.com/mikejs/factor-problems</a>