LinPHA is an easy to use, multilingual, flexible photo/image archive/album/gallery written in PHP. It uses a SQL database to store information about your pictures. It comes with a HTML based installer, so you don't need experience in setting up SQL
Simple and powerful chat client/server system for your web pages. Support channel administration, irc-like commands, connections filtering, extensive logging and much more. Works in any Java compliant web browser.
Contao Open Source CMS (fka TYPOlight)
Contao is an open source content management system (CMS) for people who want a professional internet presence that is easy to maintain. The state-of-the-art structure of the system offers a high security standard and allows you to develop search engine friendly websites that are also accessible for people with disabilities. Furthermore, the system can be expanded flexibly and inexpensively. Easy management of user rights, the Live Update Service, the modern CSS framework and many already integrated modules (news, calendar, forms, etc.) have quickly made Contao one of the most popular open source content management systems on the market.
The previous generation graphical download manager
yoDownet is an open-source && free graphical download manager project that tries to be simple and minimal, also for sake of humor it's described as "The Previous Generation Graphical Download Manager".