Scrivener is a writing tool that allows you to organise your novel into chapters and scenes and format your manuscript for publishing (among a bunch of other stuff). It can be purchased out-right for either Windows or Mac, and for iOS there is an App for writing on the go, which will allow you to synch things up. For a more expansive explaination of what it can do, please see Apple Insider’s pretty rad article (and yes I’m bringing rad back).
I have a Mac, but unfortunately an Android phone so no app for me. However, there’s a workaround that involves synching to Dropbox as a middleman. It works pretty well, especially with a light wireless keyboard if you’re on the move (provided you don’t mind using it in conjunction with a small phone screen).
I don’t work for these guys, and it’s always worth checking out the competition, so here’s a few alternatives you may want to try (and it looks like at least one of them is free, so may be a good place to start).
In time, I intend to join up the dots with these ‘tools of the trade’ blogs to present a bible of the tools and methods I use when tackling a novel-length (and indeed series-based) piece.
Of course, if you know any other great writing tools or tips, please give me a shout in the comments!