eXchaNGeR - The XML Browser
A simple and flexible browser framework for XML elements, allows for association of pluggable services with specific XML element-types.

Jaxen
Java XPath engine; mailing list, FAQ. [Apache-style]

XMLtp
A tiny XML parser/processor written in Java, supporting a subset of XML, intended for small-footprint server-side applications. [Open Source, BSD-like]

Element Construction Set
Generates elements for various markup languages. Directly supports HTML 4.0 and XML, but can easily be extended to create tags for any markup language. [Open Source, BSD-like]

Simkin
Embeddable scripting language for Java and XML. [Commercial]

Axis
An implementation of the SOAP ("Simple Object Access Protocol") submission to W3C. [Open source, Apache Software License]

DOM4J
XML framework for processing XML with integrated XPath and support for DOM, SAX, JAXP and Java 2 Collections. [Open Source, BSD-like]

J.A.D.E. - Java Addition to Default Environment
Provide: Restoration of objects whose internal state has been externalized using the XML format; Lets application decides how objects are represented using XML; Quantity classes embedding automatic error calculation (including numeric errors) - Unit class compliant with JSR-108 (for unit conversion, formatting and simplification). Generic Matrix class. [Open source, LGPL]

txt2xml
A simple Java library for parsing arbitrarily structured text input into well-formed XML output as SAX, DOM, JDOM, or through an OutputStream. [Open source, BSD License]

SAX (Simple API for XML)
Contains Namespace support and is fully configurable and extensible. [Open Source, Public Domain]

xmlenc
A fast stream-based XML Encoding Library for Java. Main design goals are performance, simplicitity and pureness. [Open source, BSD License]

JXP
Fast Java XPath 1.0 API implementation. JDK1.1 to 1.4. [Shareware]

Oracle XML Developer's Kit for Java
XML parser, XSLT processor, XML schema processor, class generator, SQL utilities, XSQL servlet, and Oracle SOAP.

Transformation API For XML (TrAX)
Offers general transformation model for converting XML documents.

JXQuick
Quick and easy XML processing. [Open Source, BSD-like]

XML Processing with TRaX
Article by Craig Pfeifer in ONJava.com. Purpose of TRaX (Java API for specifying and executing XML transformations), code example, links.

Presenting XML
A Java web application framework for presenting HTML, PDF, WML etc. in a device independent manner. The framework supports a flow of content (XML files, flat files, SQL, dynamic XML) through SAX pipelines and XSLT transforms to a device. [Open source, GPL or LGPL or MPL 1.1]

Qizx/open
A Java implementation of the XML Query Language. [Open source, GPL]

Sparta
Lightweight Java XML package that includes an XML parser, a DOM, and an XPath interpreter. Its goals are: small code size, fast execution, small memory usage, clean and simple DOM API. [Open Source, LGPL]

XMLConfiguration
A Java utility class developed by createTank to allow simple parsing of configuration files written in XML. It allows multiple methods of extraction of attributes from an XML file.