Jason Grout's description of the Sagemath Cloud:
William Stein, the lead developer of Sage, has been developing a new online interface to Sage, the Sage Cloud at https://cloud.sagemath.com. Currently in beta status, it is already a powerful computation and collaboration tool. Work is organized into projects which can be shared with others. Inside a project, you can create any number of files, folders, Sage worksheets, LaTeX documents, code libraries, and other resources. Real-time collaborative editing allows multiple people to edit and chat about the same document simultaneously over the web.The LaTeX editor features near real-time preview, forward and reverse search, and real-time collaboration. Also, it is easy to have Sage do computations or draw gures and have those automatically embedded into a LaTeX document using the SageTeX package (for example, after including the sagetex package, typing \sageplot{plot(sin(x))} in a TeX document inserts the plot of sin(x)). A complete Linux terminal is also available from the browser to work within the project directory. Snapshots are automatically saved and backed up every minute to ensure work is never lost. William is rapidly adding new features, often within days of a user requesting them.
