Science museums and science centers have been exploring the use of the Web to further their public and professional mission from the very early days of the Web's existence. From on-line exhibits to on-line experiences, these early experiments have in turn led to the robust use of this medium as a key part of the science museum world. At the dawn of the next stage of the revolution signified by the emerging Web 2.0, it is useful to take stock of where we have been and how we got here, and forecast where we might be going.