Chris Granger has open sourced the LightTable IDE with the 0.6 release. Third party plugin support was the highlight feature of the release. InfoQ talked to LightTable creator Chris Granger.
CodeMirror, an in-browser code editor, has released version 3.0, adding support for right-to-left scripts, arbitrary fonts and line heights, and inline widgets.
The embeddable open source web-based code editor ACE has reached version 1.0, coming with support for editing very large files, syntax highlighting for 45 languages, TextMate themes, Emacs and Vi key bindings, and other features.