Well, JAXP is pretty good. Personally, I'd prefer JDOM, because of the memory-cheaper document representation. You can get it at http://www.jdom.org . Its usage depends on the requirements of your application, though.
However, don't confuse JDOM and JAXP with parsers. They are XML APIs which abstract the use of the actual parser used (may it be XML4J, Crimson, Xerces, etc.).