Ymacs is an Emacs-like editor for the Web--that is, it works in a browser. Currently it’s only tested with Firefox, and it’s known to have some minor issues on Mac OS X (most key bindings flash the Edit or File menus, which seems to be a Macintosh “feature”).
Ymacs started out as an experiment and should still be considered so, but it’s currently quite functional. The main goal of the project was to make it pleasurable to write source code in the browser; using a <textarea> it’s far from convenient.
Ymacs is distributed under a BSD license.