XML Benchmark 1.2.1 is a C/C++/Java toolset for benchmarking XML parsers including libxml2, Xerces, Oracle XDK, Expat, RXP, QT, and Crimson. Benchmarks include parsing (native, SAX, DOM), DOM manipulation, schema validation, XSL transformation, and XML signature and encryption. Version 1.2.1 adds support for This release adds support for XML Security 1.1.x.
I've learned to treat benchmarks with a 20-pound bag of rock salt until proven otherwise. However, this product gets at least one thing right. It lets you plug in "Any valid XML file" so you can test parsers on the kind of documents you're interested in rather than on whatever the benchmark vendor has. Most parsers exhibit wildly varying performance characteristics depending on the type of XML document (large or small, record-like or narrative, many attributes or few attributes, etc.). It's not clear whether or not this parser can test well-formed but invalid documents.
Alexandre Brillant has released FastParser 1.6.2, a $50 shareware, non-validating, SAX parser for Java. Version 1.6.1 fixes various bugs and makes some optimizations
Brillant claims this parser is faster than Xerces and Crimson (which are known not to be the fastest parsers out there). However, his benchmarks only test one file, and it's not clear from his result whether FastParser was used in a mode that doesn't perform full well-formedness checking.