by Brian Westrich.
We coded this app as part of a coder-dojo that I attended (and mostly paired with) with my colleague Mike Calvo. The main focus of the dojo was implementing the algorithm of Conway's game of life without a graphical user interface, but since I coded my answer in ruby I couldn't resist the temptation to try to run it in a rails app.
conway logic is correct
rails app only works in single-user mode and has ugly UI. The UI looks better if you unzoom the browse (command-) to a very small size :-) ).
convert use of global ruby variable for game board to session variable (until do this, only one user can use web app at a time)
update game boards using JavaScript (so are more visually pleasing)
add an "auto-evolve" (currently have to click a link for each evolution)
improve game performance by using AJAX