Microsoft Word - Microsoft Word is a commercial word document processor for Windows.
Markdown by DaringFireball - Text-to-HTML conversion tool/syntax for web writers, by John Gruber
Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.
Typora - A minimal Markdown reading & writing app.
AbiWord - AbiWord is a free software word processor.
StackEdit - Full-featured, open-source Markdown editor based on PageDown, the Markdown library used by Stack Overflow and the other Stack Exchange sites.