Keep an eye out for JyNI ( http://www.jyni.org ), that is, for Jython, exactly what IronClad is for IronPython. At the moment, JyNI is still an alpha state.
If you just want to use some C library from Jython, just use JNA from Jython, just like with Java. If you need finer control, look at JNI or SWIG.
, JEP (https://github.com/mrj0/jep) JPY (<2 > ).