Electronic Arts is letting you play Sim City Classic for free as an online application called Sim City Live Online! The original game has been retooled for internet functionality, so all you need to play is your browser. It only seems to work in the Internet Explorer web browsers (and not all except for Netscape Navigator as EA originally stated).
1UP muses this is a marketing gimmick designed to promote Sim City 4, but it’s free so who cares? 🙂