in-memory key value server with fuzzy search capabilities
Levin is an event-based key/value server based on radix-tree (space optimized trie).
Key search can be performed with an approximate key matching algorithm based on Levenshtein edit distance.
Sedna is a native full-featured XML database management system.
Sedna is a free native XML database which provides a full range of core database services - persistent storage, ACID transactions, security, indices, hot backup. Flexible XML processing facilities include W3C XQuery implementation, tight integration of XQuery with full-text search facilities and a node-level update language.
Omseek has been renamed to Xapian. Xapian is a Search Engine Library, written in C++ with bindings for Perl, Python, PHP, Java, Tcl, C# and Ruby. It allows you to easily add advanced indexing and search facilities to your applications.