The current version is 1.1.6. 1.1.6 fixes several bugs in IEEE 754 arithmetic.
1.1 is a major upgrade that significantly improved jaxen's conformance to the underlying XPath 1.0 specification. This release is a vast improvement over 1.0, and all users are strongly encouraged to upgrade. With a few small exceptions (e.g. the document() function has moved to the org.jaxen.function.xslt package, the IdentityHashMap class has been deleted, and the ElectricXML navigator has been deleted) 1.1.6 is backwards compatible with code written to the 1.0 APIs.
The recommended build is 1.1.6:
You can grab a tarball of the current CVS head from FishEye if you like. To build Jaxen, you'll need to have maven installed. Assuming you do, you should be able to just type "maven jar" at the command line in the jaxen directory to create a JAR archive.