This extension allows you to edit (or just filter) the contents of a textarea on a web page. Since Chrome does not allow the running of an external program directly, this extension instead makes an ajax call to a web server, which can start up a graphical editor, or perform any kind of filtering you desire. The URL that is used is configurable in the options.
When a textarea receives the focus (e.g. if you click in one), an icon will pop up in the address bar. If you click it, an ajax request will process the currently-selected textarea and update the value when the request is done (e.g. when the editor exits). You can also assign a keystroke to use to activate the editor (I like Alt-Enter).
1.0.7 - Tweaked the OK/Cancel buttons on the options page.
1.0.6 - A fix for Mac OS X that made clicking on the icon not work.
1.0.5 - Include the status text in the failure alert so it is clearer what needs to be fixed.
1.0.4 - Avoid spurious failure alerts after a successful update. Added support for http basic auth (you'll need an updated version of edit-server or whatever script you're using).
1.0.3 - Added a configurable keyboard shortcut (defaults to disabled).
1.0.2 - Fixed a newly-introduced bug with the field editing.
1.0.1 - Changed event capturing method so that focusing any textarea shows the clickable icon.
The edit-server script that I wrote (in perl) for use with TextAid (the latest version outputs better status-text messages on failure, and has support for basic auth):
The servers written for the emacs_chrome project should also work (the python one did when last I looked at it, though it was only single-threaded). You could also supply your own server script, or run a CGI under a normal web server. See the options page for more information on the POST request used.