Tagsistant is a semantic filesystem for Linux and BSD kernels. It uses directories as tags and allows file tagging by simply putting files inside desired tag directories. The path you are walking by is your query, e.g. tagsistant/tag1/AND/tag2/OR/tag3/AND/tag2/. Being a low level interface, a filesystem can be instantly used by shell users, file managers, or CGI. A plug-in architecture is under development to add autotagging functionality for common files like .mp3, .ogg, .jpeg, .html, and .xml. A transparent ontology engine is also under development to allow users create a relationship schema between directories.
movemetafs is a searchable filesystem metadata store for Linux that lets users tag local files (including image, video, audio, and text files) by simply moving the files to a special folder using any file manager. It also lets users find files by tags using a boolean search query. The original files (and their names) are kept intact. movemetafs doesn't have its own user interface, but it is usable with any file manager.
Lobotomy involves many sub-projects oriented to experimentation about new design for human-computer interaction and, more generally, a new way for home computing. It involves a relational filesystem, a window manager, and many libraries, tools, and daemons to automatically extract and handle metadata.