Spoon is a PHP5 library that focuses on speed, both in page execution and coding agility. Because of its clear and logical structure, it offers a very small learning curve for both the experienced and not-so-experienced developer. Spoon provides a well documented library with a large collection of classes that you can use while building Web applications.
Analog PHP is a short and simple logging package for PHP 5.3+ based around the idea of using closures for configurability and extensibility. It functions as a static class, but you can completely control the handling of log messages through closures (aka anonymous functions), and it also comes with a dozen pre-written handlers. It is well-documented, with examples for each type of log handler, and ultra-concise. The core is literally only 43 lines of clear, non-obfuscated code, and the whole is only a fraction of the size of comparable packages (for example, 293 total lines vs 1021 for Monolog).
PIMF (Php Is My Framework) is a micro framework for PHP that emphasises minimalism and simplicity. It is based on proven design patterns and a fast object relational mapping mechanism, and is designed to be easily updated without having to rewrite your projects. It includes mechanisms for easily coupling controllers to ExtJs and Dojo.