If you would like to work on improving Emacs, please contact the maintainers at the emacs-devel mailing list. You can ask for suggested projects or suggest your own ideas.
If you have already written an improvement, please tell us about it. If you have not yet started work, it is useful to contact emacs-devel before you start; it might be possible to suggest ways to make your extension fit in better with the rest of Emacs.
The development version of Emacs can be downloaded from the repository where it is actively maintained by a group of developers. See the Emacs project page http://savannah.gnu.org/projects/emacs/ for details.
For more information on how to contribute, see the etc/CONTRIBUTE file in the Emacs distribution.