Dropbox is an application to backup data on the internet and share with your friends. On the homepage is a nice video showing the main features of the application. I like the simplicity of it all. We can easily switch between desktop and web browser interface. Looking at the video inspires me for my own user interfaces for desktop and web browser applications.
A very cool example of another way to organize hierarchical data. Folders are displayed 3-dimensional and we can click on them and the contents flies out of the folder. The new elements are displayed in front of the open folder to indicate the items belong to the folder. This application is created with Papervision 3D.