CMarkup - A C++ source class for parsing and creating XML based on the EDOM API, with articles and documentation.
CodeSynthesis XSD - A cross-platform W3C XML Schema to C++ data binding compiler. Provided with an XML instance specification (XML Schema), it generates C++ classes that represent the given vocabulary as well as parsing and serialization code. [Open Source, GPL]
RapidXml - An attempt to create the fastest XML parser possible, while retaining usability, portability and reasonable W3C compatibility. It is an in-situ parser written in modern C++, with parsing speed approaching that of strlen function executed on the same data. [Open Source]