In another step to create consistency between Microsoft products, Outlook.com now includes the App Launcher that is part of Office 365. One click on the App Launcher opens the view shown below. Merely click the destination and it launches!
The App Launcher makes it easy to toggle between your calendar, OneDrive and the Office Online applications. If you are using the free Outlook.com email service (@outlook.com, @hotmail.com, @live.com, or @msn.com), see how easy it is to use.
If you click the App Launcher and change your mind about leaving the service you are currently, merely click in another spot on the page or click the Launcher again to close it.
Read the complete announcement at the Office Blog, Toggle between Outlook.com, OneDrive and Office Online with the new app launcher.