There are a range of demonstrations of PyFeyn's capabilities on the examples page. The current PyFeyn version is 0.3. You can get it from the HepForge downloads area. As a source tarball. You can also use the Python "easy install" system - see the PyFeyn entry on PyPI. Or you can check it out directly from HepForge Subversion. If you fancy following the bleeding edge releases. Please see the installation guide page. As its rendering back-end, so you'll need to have PyX installed before PyFeyn will work.