Office Web Apps Server is an installable component that allows enterprises to use browser-based versions of Word, PowerPoint, Excel, and OneNote – similar to what's available in Office 365 and Office Online.
Released in October of 2012 to the Microsoft Download Center, companies have been able to download the product for free. On November 24, 2014, Microsoft will be removing it from the Download Center and making it only available through the Volume Licensing Center.
If this is something you use, or want to use, I'd suggest grabbing it now while the download link is still available:
Learn how to set it up: Deploy Office Web Apps Server