Well... although far from complete, I am currently the lead developer for a new cross-platform open source project:
Here is a screenshot:
Some of the features are more complete than others... but here are the intended goals:
- Syntax highlighting (pretty much complete)
- Project organization (partially implemented)
- Auto complete (including completion for common JS frameworks like jQuery, etc.)
- Build system (for combining files, minification, etc.)
- Extensible GUI (via JavaScript extensions)
- Line numbering (sort of complete), word-wrap, configurable colors for syntax highlighting