Ariadne is a Web Application Framework and Content Management System built with PHP. It allows you to build complex Web applications and sites with ease. It takes care of the mundane stuff like internationalization, security, user management, templating, data retrieval and storage, caching, and site management. It stores content in a structured object store that can be accessed through an extensive filesystem-like API.
LimeSurvey (formerly PHPSurveyor) is a Web application that interacts with MySQL, MSSQL, or Postgres to develop surveys, publish surveys, and collect responses to surveys. Once a survey has been created, data can be inserted into the survey either by a "pretty" public screen which presents each question one at a time, or by a quick and nasty data entry screen. It includes the capacity to generate individualized "tokens", so that invitations can be issued to participants. It also has the capacity to set conditions on whether questions will display (branching), numerous question types, and a basic statistics function.
Simple Groupware is a complete enterprise application offering email, calendaring, contacts, tasks, document management, synchronization with cell phones and Outlook, full-text search, and much more. Simple Groupware combines standards like RSS, iCalendar, vCard, IMAP, POP3, SMTP, CIFS, CSV, WebDAV, LDAP, and SyncML under one platform. Unlike other groupware software, Simple Groupware contains the programming language sgsML to enable the quick customization and creation of powerful Web applications.
Kronolith is the Horde calendar application. It provides a stable and featureful individual calendar system with integrated collaboration and scheduling features. It makes extensive use of the Horde Framework to provide integration with other applications. It implements a solid, stand-alone calendar system, allowing repeating events, all-day events, custom fields, keywords, shared calendars, iCalendar support, generation of free/busy information, and managing multiple users through Horde Authentication.
Roundcube Webmail is a browser-based, multilingual IMAP client with an application-like user interface. It provides the full functionality you expect from an email client, including MIME support, address book, and folder manipulation. High extensibility is granted by the plugin API and the user interface is fully skinnable using XHTML and CSS 2.
Bitcoin is a peer-to-peer electronic cash system that is completely decentralized, without the need for a central server or trusted parties. Users hold the crypto keys to their own money and transact directly with each other, with the help of a P2P network to check for double-spending.