SimplePie – RSS and Atom Parsing
http://simplepie.org/

SimplePie is a very fast and easy-to-use class, written in PHP, for reading RSS and Atom syndication feeds. By keeping it simple, and focusing on what’s important, we’ve built a pretty sweet little API. SimplePie’s focus has been two-fold: speed and ease of use, and has been very successful on both fronts. This has been added to the presentation resources of Bots, Blogs and News Aggregators.