Galax
- An open source development effort whose goal is to provide a fully compliant implementation of the family of XQuery working drafts. Includes an online demo.
- http://www.galaxquery.org/

DataDirect XQuery
- Java software that implements XQuery and XQJ standards, allowing developers to access both relational and XML data sources.
- http://www.xquery.com

oXygen XML Editor / XQuery Debugger
- XML Editor with editing and debugging support for XQuery. Allows XQuery execution against multiple XML databases: eXist, Berkeley XML DB, X-Hive, MarkLogic, TigerLogic.
- http://www.oxygenxml.com/xquery_debugger.html

X-Hive's XQuery demo
- An on-line demo that allows you to run queries against a sample XML database.
- http://support.x-hive.com/xquery/

Qexo (Kawa-XQuery)
- A partial implementation of XQuery. It compiles queries down to Java bytecodes using the Kawa framework.
- http://www.gnu.org/software/qexo/

Derby
- GAEL Consultant's integrated Java environment for data visualization uses XQuery as its query language.
- http://www.gael.fr/derby/

Xquery Lite
- A query language for XML, based on XQuery 1.0. Includes an implementation for PHP.
- http://phpxmlclasses.sourceforge.net/xquery_lite.html

XQuench
- A project to create an open-source XQuery parser and engine in Java.
- http://sourceforge.net/projects/xquench/

XQuantum Database
- Cognetic Systems' research implementation (in Java) of a subset of XQuery, along with its type inference system.
- http://www.cogneticsystems.com/xquery/xquery.html

XML Query Engine
- Fatdog Software's full-text XQL search engine, with partial support for XQuery. Eval version available for download.
- http://www.fatdog.com/

Xcache Rainbow Project
- A web-based XML query engine and tools, which use a cache of results from previous queries.
- http://davis.wpi.edu/dsrg/

Stylus Studio: XQuery Tools
- Development tools for editing, mapping, debugging, and profiling (benchmarking).
- http://www.stylusstudio.com/xquery.html

SQLSummit Catalog of XQuery Engines, Processors and Providers
- This catalog of XQuery implementations includes processors, embeddable engines and database managers. Includes download links and contact info.
- http://www.sqlsummit.com/XQueryProv.htm

CL-XML
- James Anderson's collection of Common Lisp modules for XML includes XQuery support.
- http://pws.prserv.net/James.Anderson/XML/