As soon as there's enough to actually play and potentially enjoy the experience
you could submit it to JGF (see my sig for URL).
Although the games are all lumpted together at the moment, we hope to soon have them split into "in progress" and "complete". As long as it's fun/interesting/good, we'll accept anything.
Although...we reserve the right not to accept things that don't use webstart. There are tutorials on the site showing you how to webstart your game in just a couple of minutes, so there's no excuse