Associative Indexing Service: An application for easy adding of keywords for archives and any resources for fast future access. It is an extension of associative memory, associative helper and also may be used as a personal search engine.
BDDBot: A web robot, search engine and web server written in Java and available under GPL. Includes related resources. [Project no longer actively updated]
DataparkSearch Engine Tool: Open source search engine tool released under GPL and designed to organize search within a website, group of websites, intranet or local system.
Egothor: A cross-platform, full-featured text search engine written entirely in Java. It can be configured as a standalone engine, metasearcher, peer-to-peer HUB or used as a class library.
JXTA Search: A distributed search system, designed for peer to peer networks and web sites.
KDE GUISearch: Allows searching the KDE project CVS repository using GUISearch, a new kind of tool for finding code by looking at the applications' GUI text messages (e.g., "Undo") and returning associated callbacks/slots (e.g., slotUndo()).
Nutch: Effort to implement a prototype of an open source web-search engine.
Open Source Search: Resources, ideas and news site for developing next generation open source search engines. Includes relevant source libraries and white papers.
Open, Distributed Web Search: Article that discusses the concepts of an open source, community-run, distributed web search service. One possible architecture is presented, although no working code or implementation exists.
OpenWebSpider: An open source web spider and search engine. Includes demo, source code and screenshots.
Oxyus: An open source search engine written in Java, aimed to provide a search button for websites. Includes related project news.
Search Tools Listing: Open Source Search Engines: A listing of open source indexers, including links to related articles.
Sourcebank: Full-text search engine for source code.