Open Source Google Reader Alternative – Tiny Tiny RSS
Tiny Tiny RSS is an open source and web-based feed reader application that offers a desktop-like user experience.
It is built with PHP, uses MySQL or PostgreSQL for storing data and makes use of the Magpie and SimplePie libraries (check PHP RSS Parsers) for fetching the feeds.
The interface is completely Ajaxed, there is support for RSS, RDF + Atom and protected/authenticated feeds can be read as well.
Tiny Tiny RSS not only fetches data but can re-publish them as well (again as a RSS feed). The data is also reachable via a JSON-based API.
The application supports multiple users, it is multilingual and has a mobile-version as well.
And, there are many other features like OPML import/export, keyboard shortcuts, duplicate content filtering or article scoring.