Code Mirror (online code editor) is great, I used it on TeamMentor (TM) to create an web editor for server side content (one of the gems hidden inside it :) ).
Code Mirror was really easy to integrate and you can see it in action below or at: jsbin.com , sourcelair.com or wescheme.org
Yes, I can edit HTML directly from the browser :)
This is a great 'admin' feature and has helped me to solve a lot of problems in real-time on remote deployments. It also has a number of security features/requirements, which I want to cover on later posts.
Btw, I would like to package this module as a separate project, since this HTML/Ashx code editor is already packaged as a stand alone unit inside TM (if anybody wants to do it ping me directly, this would be a great mini-project to do)
At TM, the code is the WebEditor folder and the real action happens inside the WebEditorService.ashx file.
Here it is in action: