The ICFP '02 contest have listed the number of entries per language.
Ruby is pretty high up the list with a whopping 3 entries but nowhere near
close to Python or Perl.
Hopefully this robot contest has made it easy for bright Ruby minds to
compete :-)

      Java  28
      C++  22
      C  20
      Caml  19
      Python  16
      Perl  11
      Haskell  10
      Scheme  7
      Common lisp 4
      Ruby  3
      Dylan  2
      Erlang  2
      Mercury  2
      Ada  1
      Delphi  1
      Forth  1
      Icon  1
      Prolog  1
      Smalltalk  1
      Sml  1
      Total  136


http://merd.net/pixel/language-study/icfp-figures.html