SimplePie is a RSS parsing script used all around the web, for showing content from RSS feeds and sometimes to mash them together. It works standalone, but is also shipped with some publishing platforms, like WordPress for example.
Unfortunately, the lead developers Ryan Parman and Geoffrey Sneddon have decided to cease development of SimplePie. The project will be moved to GitHub and hopefully someone will pick up the reins, since this is one of the best solutions for working with RSS feeds available.
Read the announcement post for more on why this came to be.