BlackRay is a relational database system designed to offer performance features commonly associated with search engines. It offers SQL support and sophisticated operational and management features. Load-balancing and operational stability by means of N+1 redundance are included. BlackRay is called a "Data Engine" since it combines traditional, relational database features and SQL with the power and flexibility of search engines. It is a true hybrid, offering transaction support, data-versioned snapshots, and sophisticated function-based indices. Wildcards, phonetic, and fuzzy logic searches are supported, as well. BlackRay supports a subset of the SQL92 standard and provides JDBC/ODBC/native driver options via the PostgreSQL protocol, in addition to an API based query option. The project is released under the GPLv2, with some drivers available under BSD-style licenses. Commercial support contracts are available as well.
XapianFu is a Ruby library for working with Xapian databases. It builds on the GPL licensed Xapian Ruby bindings, but provides an interface more in-line with "The Ruby Way"(tm) and is considerably easier to use. For example, you can work almost entirely with Hash objects, and XapianFu will handle converting the Hash keys into Xapian term prefixes when indexing and when parsing queries. It also handles storing and retrieving hash entries as Xapian::Document values. XapianFu basically gives you a persistent Hash with full text indexing (and ACID transactions).
Seeks is a Web search proxy, meta-search engine, and real-time P2P pattern matching network for social Web search. Its specific purpose is to regroup users whose queries are similar so they can share both the query results and their experience with these results. On this basis, Seeks allows true real-time, decentralized Web search to emerge. In the long term, there is no need for Web crawlers and third-party Web indexes. Most importantly, Seeks is intended to become a flagship for a fair, transparent, user controlled machinery for searching the Web over the Internet.
Arch is an extension of Apache Nutch (a popular, highly scalable general purpose search engine) for intranet search. It includes blind test evaluation tools for comparing to other search engines. Arch has many features critical for corporate environments, such as document level security.