YAPAB is an address entry collection system. It has many features including user accounts with adjustable permissions, multi-language support, IM between users, import/export functions for common file formats, group actions to collect entries in reachable places, and the ability be used under any browser and operating system.
Yawiki is a powerful Wiki system for collaborative document generation. It supports both anonymous and authenticated users. It uses an AreaMap page to generate a hierarchy of pages and navigational elements. It supports page-level access control lists. There is an optional comment system built-in, as well as RSS feeds for individual public pages.
Yellow Duck Weblog is a full blown Weblog application written using the Yellow Duck Framework. It features photo blogs, categories, static pages, and links. It also has full blown statistics built into the easy-to-use management interface. The application can easily be translated, and has support for skins by means of Smarty templates.
ZebraFeeds is a Web-based RSS/Atom aggregator. It can be integrated into your Web site or blog with minimal effort and a high level of customization. You can also use it as a personal Web-based news aggregator with a reasonably convenient user interface inspired from modern aggregators.
b2evolution, is a multi-lingual, multi-user, multi-blog engine. It was developed to provide a free, feature rich, extensible, and easy-to-install solution for efficient Web publishing of information ranging from professional news feeds to personal weblogs. b2evo can easily be installed on almost any LAMP (Linux, Apache, MySQL, PHP) host in a matter of minutes.
BaseballNuke is a module for PHP-Nuke that allows for the administration of a baseball team. It manages a team's roster, stats, and schedules. It simplifies team administration and communication to fans. There are plans to expand this module to include league management and to work with other open source CMS projects.
bbgun moves phpBB forums to WordPress blogs. bbgun pulls a forum entry from the phpBB database, translates the text (bbCode to strict XHTML), date, and other fields, and pushes the translated entry into the WordPress database. With bbgun, you can move individual posts, move entire threads, move only certain users' posts, map phpBB users to WordPress authors, and specify WordPress categories for the new entries.