Many of the writing apps out there attempt to give you a structure to hang your words on. Some try to get you to break things down to scenes, some break the storyline down into conflicts... Some give you ways to organize your background notes... I've never really found an advantage to most of these features except maybe the note organizing if only to keep a "foreign words" (SF / Alien languages) dictionary or give thumbnail character biographies so I can keep my characters and their histories straight.

Mostly I've found that fussing over a writing app is a way for the subconscious mind to resist putting words on a page. At one point in time,  I used to write everything long hand on paper and then put the second draft into the computer. But having gotten older and less nimble with my fingers [driving a pen or pencil is hard work now!] most of my writing starts in:

Textpad -- a programmer's text file editor that also has other features [no grammar checker unless you are writing in a programming language]. It does colors and has a highly capable macro feature. It has a spell checker --  but no grammar checker  -- after all mangling grammer and spelling into a "dialect" is one of those things a writer may be required to do sometimes in dialogue for authenticity.

Such dialects tend to give auto-grammar correction application fits [It would have choked on Heinlein's "The Moon is a Harsh Mistress"]... or you end up with dialogues that read like cell phone text messages with auto-complete turned on. I've been using Textpad since version since about 1998 [it's now version 7.1... registration allows free updates to all future releases]. Betterto trust a human editor.

If the story turns out to be is good enough to need be formatted then I'll move it over to MS Word or LibreOffice [a fork of Oracle / Sun OpenOffice]. The point for a writer is after all to write... I figure that it is better to write something that may have grammar and spelling issues than to write nothing at all... After all that's what the second and third draft are all about.

http://www.textpad.com  $27 or 16.5 Pounds

There are some other free text editors available which are just as capable as Textpad. So if you'd like something like that, try Notepad++ http://notepad-plus-plus.org/

Just remeber these were designed to write and not necessarily do fancy things like grammar checking

A free Windows file diff app can be found here: http://winmerge.org  -- a great way to help merge different versions of the same story into one version.

yWriter - yet another writer / story plotting program for Windows. . yWriter fully functional and free  and has a low registration fee ($11.95 if you want to register - the author of the app would appreciate it).  If you use Linux, it will install via WINE or Crossover Office (I did this on an HP Mini netbook that has Crossover Office installed on a  Kubuntu Linux install. Works just fine. The downside is that it closed source and there's only one developer.

http://www.spacejock.com/yWriter5.html

The developer of yWriter recommends  "Schivener" if you are a Mac user. Schrivener can be found here:

http://www.literatureandlatte.com/scrivener.php they now have windows version $40 for Mac or Windows

Celtx -- A scriptwriting  app which will do all kinds of document formating [Film Script, Audio Script, Storyboard, Comic Book, Theater (Play). Celtx is a specially modified version of the Firefox browser to turn it into a "cloud aware' collaborative script writer / sceduler / planner.

Celtx was designed to do media scripting so includes features not found in "normal" writing apps. Among other things it has scheduling features, casting,  it has some "database" like functions where character bios, images, job assignments, etc can be stored.

There are plugins -- "cork board plotting" (aka 3x5 card plotting), "full screen mode" which allows choice of colors and an add-on of icons / images all for a low price). The version I use is version 2.7  but the current version is much  more internet "cloud" focused (after all selling clouds seems to be all the rage and guarantees the app developers a revenue stream) -- you can "rent cloud space" for about $10 a month of $70 a year [the price has gone up]...It has the advantage that you won't lose your work to a local computer crash on the other hand it is on-line and is subject to all of the current snooping of internet traffic.

http://www.celtx.com The basic editor is Free... up to $14.95 for a plugin package.... or monthly / yearly fee if you want the cloud versions

There are several others that I have tried:

Dramatica - which is a story structure application that forces you to think of your story in the terms of the Dramatica idea for story [see http://dramatica.com/theory for an explanation]... I bought it a long time ago [the late 90's] and while it might be useful for story analysis, I found  (at least for me) it was useless as a writing app or as a way to put together a story. You spend more time trying to wrap you thinking around the theory and so never get anything written.

Storybook Pro -- very similar to yWriter above. I actually bought a license for version 3.2 but did not really use it the way intended. Recently the program's publisher seems to have gotten into trouble with the tax authorities in Switzerland who seized the web site and so the "pro" version is unavailable...

BUT since the "basic version" was open source software that was hosted on Sourceforge, someone has stepped forward to restart the opensource  project with the goal of adding the pro features as free open source software. requires Java to be installed... The basic version can be found here:

http://sourceforge.net/projects/ostorybook/

Other tools:

Microsoft OneNote -- just for research notes can also be used as an OCR app to convert images of text to in text... it's pretty much useless for anything else.

Plotto -- Not an writing app but a e-book of a book written in the 1930's  with an algorithm for generating plot ideas / plot threads... Available at Amazon for $3.99

http://www.amazon.com/Plotto-The-Master-Book-Plots-ebook/dp/B008913086/ref=sr_1_2?ie=UTF8&qid=1387004160&sr=8-2&keywords=plotto

TableSmith: written as a role playing game aid for Windows this app can generate names [modern, ancient, elven, etc.] , places, and so forth. Low registration fee of $10.

http://www.mythosa.net/Main/TableSmith?from=Utils.Html

regards!