Time to share those Open-Source solutions to web development problems you've found with the rest of us. I'll kick off with these six -
FCK Editor
"This HTML text editor brings to the web many of the powerful functionalities of known desktop editors like Word."
PHPDig
"PhpDig is a web spider and search engine written in PHP, using a MySQL database and flat file support."
OSCommerce
"osCommerce is an online shop e-commerce solution under on going development by the open source community."
TextPattern
"A flexible, elegant, easy-to-use content management system for all kinds of websites, even weblogs."
dotProject
"dotProject is a PHP web-based project management framework that includes modules for companies, projects, tasks (with Gantt charts), forums, files, calendar, contacts, tickets/helpdesk, multi-language support, user/module permissions and themes."
phpDocumentor
"phpDocumentor is the world standard auto-documentation tool for PHP." (think JavaDoc)