mediadbs is a database system built around MySQL, with the ultimate aim being the categorization of diverse electronic media, with tools to extract the data from the files, and to make the data available in many ways. Currently this is limited to mp3 id3 tags, and a Web-based output.
OpenGuides is a wiki-like package for maintaining a collaborative city guide. It is written in Perl and runs as a CGI program, and uses either the MySQL, PostgreSQL, or SQLite database. It offers features over a "normal" wiki such as metadata management and a "find nearby things" function. The look and feel is highly customizable thanks to use of the Template Toolkit.
Photopub is image publication software designed primarily for easily maintaining a Web site of pictures taken with digital cameras (although it can be used for arbitrary images, it has some features which make it most suitable for them). It runs as a CGI script or under mod_perl, and is fully themable and highly customizable.