AUCTeX is an extensible package for writing and formatting TeX files in GNU Emacs and XEmacs. It supports many different TeX macro packages, including AMS-TeX, LaTeX, Texinfo, ConTeXt, and docTeX (dtx files).

AUCTeX includes preview-latex which makes LaTeX a tightly integrated component of your editing workflow by visualizing selected source chunks (such as single formulas or graphics) directly as images in the source buffer.