Fiddle Is a Collaborative Markdown Tool for the Web
When it comes to co-authoring, Google Docs is the best choice for most. But if you’re looking for something simple that doesn’t require a login, Fiddle is a simple Markdown editor for co-authoring.
On the surface, Fiddle is a fairly simple Markdown editor that exists in your browser and can save Markdown files both online and in your Dropbox. Then you can share the link with someone and Fiddle will create a new document for editing. Every time you share a link, a new version of the file is created. So it doesn’t have the same type of live editing as something like Google Docs, but file versioning is an approach that can be useful for other types of projects.
Fiddle | via One Thing Well