Current Web technologies allow developers to create rich Webapplications. Unlike desktop applications Web 2.0 allows to create programs by easily linking several existing components. This approach, also known as mashup, allows to use JavaScript to connect web-services and browser components together.
I have extended this development method by bringing 3D and virtual world networking components into the browser. This allowed me to create Virtual Worlds Web-applications similar to Second Life. I have wrapped opensource Sirikata platform for virtual worlds into a Web-service component, created XML3D rendering component, combined them with other browser services and thus created fully-featured 3D world application right inside of the browser.