Excelent Addition to Emacs
Now that I've been using auctex for more than 3 years, I think that it is one of the first packages that I include in my systems, right after I install Emacs.
It is so nice to use and the current improvements being made just make it even better. Highly recommended for anybody that uses LaTeX with Emacs.
An open, cross-platform journaling program.
A scientific plotting package.