Searching for a webbased diagram editor

I really like the Google Docs application. Working together with a team on a spreadsheet is really useful for status overviews. Love to see that this is working without browser plugins. I was really surprised to see the direct updates when a colleague was editing a cell of the shared spreadsheet.

Working together with web based collaboration tools makes it easy to share information directly to each other. At work we use Drupal to share information. Adding new content is easy and you can do it anywhere you want without installing software. Only an Internet connection is required.

When it comes to software development, I miss the functionality of creating diagrams within the web based collaboration tools. For example the steps I have to take to show an UML diagram within the webpage document:

1. Create an UML diagram with an external application (Enterprise Architecture for example)
2. Copy and paste the content of the diagram to an application which can save it as an image (Photoshop or MSPaint)
3. Save the image
4. Within the webbased collaboration tool use the browser upload functionality.
5. Finally add the image to the document.

What if i made a mistake or want to update these diagrams? Or what if a colleague wants to update them?

It should be possible to make such an editor. UML can for example be converted to XMI which makes it possible to use for a webbased diagram editor to work with. I tried searching for such a web based tool but at this moment could not find anything useful. Do they exist? Or should i try to create a proof of concept to see if it is possible?

BTW: besides creating diagrams online, I also want to see the functionality of pasting an image within the webdocument. Clipboard functionality is limited inside a browser (because of security reasons). Would this be possible by the use on a Firefox plugin? The website should have some (AJAX) method implemented which accept a BASE64 encoded string containing the image data. This image data was stored on the clipboard. Don’t see any security risks because the user triggers the paste operation and websites only implements these methods on parts for which the user is logged in. So another research topic: is a FireFox plugin capable of making access to the clipboard?