Sony plans to launch an online marketplace where fans of its multiplayer games can buy and sell virtual artifacts, a practice it previously discouraged. <A HREF="http://news.zdnet.com/2100-1040_22-5678052.html?tag=zdnn.alert">The Station Exchange site,</A> announced Wednesday by Sony Online Entertainment, is apparently in response to the growing underground market for such items. Planned for launch in late June, the site will first offer subscribers to Sony's "EverQuest II" the option to buy, sell or trade the right to use specific characters, items and online funds that they have earned playing the video game.