Papel is a wonderful windows freeware program created by Michael O'Donnell to facilitate the writing of novels. The project was unfortunately abandoned and his site taken down; and since there is no source code, it cannot be improved. Fortunately, Michael offered what he had of his site and program files to be mirrored elsewhere. There is a mirror of Michael's original site hosted here. I invite you to read his words and to try out the program.
Romanzo is an open source software project currently in the requirements planning phase. When completed, it will offer much of what Papel promises but with several key advances.