In case you missed it, Microsoft Office Mobile for Android or iOS smartphones used to be free only with a qualifying Microsoft Office 365 subscription, but now they're just free! Period! No Office 365 account required.
- Microsoft Office Mobile for iOS Smartphones - FREE!
- Microsoft Office Mobile for Andorid Smartphones - FREE!
You can of course still integrate the Office Mobile apps into your Office 365 experience.
This change toward a free version of Microsoft Office Mobile for smartphones came about with the delivery of the new Office for iPad apps several weeks ago. Those do require an Office 365 subscription for full features. Microsoft may be working on a tablet version of Microsoft Office for Android, but as of yet Microsoft Office Mobile for Android smartphones is the only installed mobile option from Microsoft.
In addition, you might be interested in Microsoft's free, browser-based version, Microsoft Office Online.