Mac: Write!, a good-looking writing tool (previously Windows-only), now has a Mac version that brings all of its best features over, including auto-saving, cloud-synced documents, offline editing, day and night editing themes and unlimited undo. Everything that made Write! great in Windows is available on the Mac. Even when offline, Write! autosaves everything you do, and lets you undo as many times as you like, even across computers. If you pick up where you left off on your Windows PC, you'll be able to undo the last thing you did — or the last ten things — you did on your Mac. The app features smarter auto-complete, which can suggest words based on your typing history; supports Markdown, Wiki and Textile syntax if you're into them; and can be tweaked to run in a thin, menuless tabbed interface or a more Word-like menu-rich UI depending on what you prefer.
In addition to basic editing features, Write! also lets you publish your documents right to your social accounts, or email them privately from within the app. It even has a high-focus mode where it fades out everything — including other paragraphs in your document — so you focus right on what you're writing, right now.
Write! is free, and most of its features are free, but many (like cloud saving and unlimited undo) are only free for a trial period after you sign up. After that, if you want them (and you don't need them to use the app, but they are useful,) you'll need to sign up for a ($US4.99 [$7]/mo) Pro account. Hit the link below to create an account and give the new version a try.