Red-Piranha is a search system that can actually learn what you are looking for. It can be used as a Web page, command line, or XML-WebService, so it will work with most languages, including Java, Perl, C#/.NET, and PHP. It includes learning abilities for the Desktop/Internet search functionality. All feedback from the user is stored in (editable) XML and RDF, and is used by the system to improve the quality of searches.
SCAN is a personal information retrieval framework, combining search, text analysis, tagging, and metadata functions for document collections management. SCAN is a component-based software using a number of plugins for specific features. The basic SCAN platform can be easily extended with plugins for different document formats and document location types.
SRESI is a smart bookmark manager. It currently sports both a command-line and a PHP interface. It works with both the standard hierarchical trees and the new and fashionable tagged bookmarks. It was developed as a way to interface both representation systems. SRESI can use Del.icio.us, Mozilla, Opera, and XBEL bookmarks, and handles a few more exports besides. Directories and tags are used equivalently, and the final hierarchies are inferred from actual tag use.
Samizdat is a generic RDF-based engine for building collaboration and open publishing Web sites. It provides users with the means to cooperate and coordinate on all kinds of activities, including media activism, resource sharing, education and research, advocacy, and so on. It intends to promote values of freedom, openness, equality, and cooperation.
Strigi is a desktop and indexer independent desktop search engine. Its main features include very fast crawling, a very small memory footprint, no hammering of the system, and pluggable backends (currently clucene and hyperestraier was provided). Communication between the daemon and search program is done over an abstract interface which is desktop independent. A small Perl program with an example of how to query the database is included along with an example KDE client application and a KIO interface.