MojoMojo is a Web2.0 wiki with AJAX live preview, hierarchical structure, tags, diffs, pluggable syntax, permissions/ACL, attachments, RSS feeds, a photo gallery, edit conflict resolution via 3-way merge, themes/skinning, localization, built-in full-text search, and a reverse index. Since it's built on top of the Perl Catalyst Web framework, MojoMojo supports any Web server, and includes its own standalone one. It also support any database backend supported by the DBIx::Class ORM, and has been successfully tested with PostgreSQL, SQLite, and MySQL.
mixd.tv helps you discover videos from your favorite online sources. You can use text searches or browse channels, add your favorite videos to the video library or publish them to the mixd.tv community in a playlist or via Facebook, and subscribe to channels and receive automatic updates.
Adapro is a customizable multi-user word processor originally geared towards users with a learning disability or developmental disorder, such as dyslexia or autism. Hence its array of assistive features, including inline representation of words through pictograms, a virtual keypad with configurable phrase buttons, a dyslexia-friendly font, PBDQ, and high-contrast modes. The editing interface can be customized on a per-user basis, and documents produced with it can be exported to RTF for further editing in OpenOffice or other software. If Java 6 is on the system, it doesn't even require installation.
TinyIB is a lightweight PHP image board which emulates the functionality of 4chan. If you use MySQL or SQLite, you can use it to create an efficient setup able to handle large amounts of traffic. If you don't use a database, it can store posts as text files for a portable setup capable of running on virtually any PHP host.