For those of you who have ever played Yu-Gi-Oh! this is Pokemon's equivalent to DN. For those of you who haven't Pokemon Showdown is a new website (made by the guys at Serebii, I think) which is really neat. It allows you to choose any Pokemon in the National Pokedex (including a few popular fanmade ones) and take them into battle in an environment surprisingly similar to the games. My favorite mode, however, is Random Battle which gives you a random team of six Pokemon then has you duke it out with another trainer with random Pokemon.
The website doesn't support accounts yet (as far as I know) so you might lose your teams if you delete your cookies but I'm curious to see who would be willing to try this out with me. It's totally free (of course) and pretty darn fun. The only downsides seem to be single battles only, the fact that it's still in beta and the fact that you can't have an account to save things on.
http://pokemonshowdown.com/ (http://pokemonshowdown.com/)
This is actually really quite good =D