Projects that lived
Tarzan
https://aws.amazon.com/sdk-for-php/An SDK for Amazon Web Services. Became the official AWS SDK for PHP in 2010.
SimplePie
https://github.com/simplepieA library for parsing RSS and Atom feeds in PHP. Became wildly popular and is now integrated into WordPress.
Projects that died
Blocker
Blocked robots from visiting your website. Helped websites avoid referrer spam.
FeedParser
A pre-cursor to SimplePie, FeedParser parsed RSS 2.0 feeds in the browser with JavaScript.
Blogroller
This was the project I was building SimplePie for in the first place. No code ever got written because SimplePie became so popular.
RequestCore
This was discontinued after discovering Guzzle.