I have Visual Studio Online (now VS Team Services) account as a part of my MSDN subscription. I managed to create a project there, set a workspace in my local Visual Studio 2013
The Visual Studio Monaco editing experience is currently available on a number of Azure Websites. A quick introduction and getting started can be found on Channel9:
http://channel9.msdn.com/Series/Visual-Studio-Online-Monaco
Especially the "First Steps" video walks you through the steps of setting this up:
http://channel9.msdn.com/Series/Visual-Studio-Online-Monaco/First-Steps
This is (not yet) available for non-azure website projects, but this is where things are heading without a doubt. I can't wait to get my hands on it.