Eric said Web 3.0 will be "applications that are pieced together" - with the characteristics that the apps are relatively small, the data is in the cloud, the apps can run on any device (PC or mobile), the apps are very fast and very customizable, and are distributed virally (social networks, email, etc).
Web 2.0 is a term often used today to define a second generation of web development and design-it is a far-reaching term that encompasses a great number of new ideas, technologies, communities, and services.