A new, web-based Instant Messaging application for iPhone has appeared online. iPhoneChat is from the same people that posted the first web-based iPhone-specific application, iPhoneDigg. iPhoneChat allows users to log in to their AOL IM account, see their buddy list, and features support for multiple conversations — although right at the moment, opening more than four chats at once “gets unruly.” The app currently works in Firefox…