As the title says, an MUD has been made in Flash! http://www.newgrounds.com/portal/view/348214
As far as I can tell, this is the best website to play it at.

Admittedly, there are not many players, but that can hopefully change, if you guys try it out. Now, please understand that there are no graphics, only text (It is an MUD). If you can stand that, then I'm almost positive you'll enjoy this.

PS: Maybe post your IGNs so we can know who's from OnRPG. Just a thought.