I have recently added an editor for ReStructured Text to ETS. As you can see in the screenshots below, the editor is largely composed of two panes, with the left pane containing an editor for the RST and the right pane displaying that RST as HTML. The HTML preview can be generated by vanilla docutils or by Sphinx, and this is configurable within the application.
The HTML preview is updated live as you type. Because all RST processing occurs in a separate helper process, the application remains snappy even when editing large documents.
Both the Qt4 and the wxWidgets backends of Traits UI are supported.
Note: The editor requires the latest trunk versions of Traits and Traits UI. For more information on running the application, please see the readme file.
Edit: With the recent release of ETS 3.3.0, the trunk version of ETS is no longer required to use the editor, as it is included in that release. That being said, if you update the editor to its latest trunk version, you must also update Traits, TraitsGUI, and TraitsBackendWx/TraitsBackendQt to their latest trunk versions.