LibreOffice - Free office suite, open source, and compatible with .doc, .docx, .xls, .xlsx, .ppt, .pptx files. Updated regularly – download for free. Originally based on OpenOffice.org.
Airborn - Create and edit documents online without sacrificing your privacy
ONLYOFFICE - ONLYOFFICE is a complete office and productivity suite.
Apple iWork - iWork is an office suite by Apple.
Apache OpenOffice - Apache OpenOffice is an open source, office document productivity suite.
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.