Does your neck hurt from turning between previewer windows and the source too often? This Elisp/LaTeX package will render your displayed LaTeX equations right into the editing window where they belong.
The purpose of preview-latex is to embed LaTeX environments such as display math or figures into the source buffers. By mouse-clicking, you can open the original text. After editing, another click will just run the region in question through LaTeX and redisplay the new results.