Wikipedia
SageMathCloud
SageMathCloud is a web-based cloud computing and course management platform for computational mathematics. Part of the Sage project, it supports editing of Sage worksheets, LaTeX documents, and IPython notebooks. SageMathCloud runs an Ubuntu Linux environment that can be interacted with through a terminal, additionally giving access to most of the capabilities of Linux.
SageMathCloud offers both free and paid accounts. Subscriptions starting at $7/month provide internet access and more storage and computing resources. One subscription can be used to increase quotas for one project used by multiple accounts. There are subscription plans for courses. Over 200 courses have used SageMathCloud.