Mostly free, these pieces of software come by way of Dustin M. Wax says

Since I’ve been eating, drinking, breathing, and sleeping “writing” all week, it seemed natural to pull together some of the tools, sites, and tips I know of that can help make writers more productive, organized, and creative.

If you like tools and sites to help you get creative or solve your writing challenges, check out the lifehack posting for The Ultimate Writing Productivity Resource.