Pyrex
- A Python-like language for writing extension modules.
- http://www.cosc.canterbury.ac.nz/greg.ewing/python/Pyrex/

Java-Python Extension
- A seamless, complete, and efficient integration of Java and standard Python (C Python). JPE provides Java access to Python's native extension, and Java's Swing to Python developers. [Open Source, MPL]
- http://sourceforge.net/projects/jpe

PyObjC
- Provides a bridge between the Python and Objective-C programming languages. [Open Source, MIT license]
- http://pyobjc.sourceforge.net/

Boost.Python
- A C++ library which enables seamless interoperability between C++ and the Python programming language.
- http://www.boost.org/libs/python/doc/

SIP
- A tool that makes it very easy to create Python bindings for C and C++ libraries.
- http://www.riverbankcomputing.co.uk/sip/index.php

SWIG (Simplified Wrapper and Interface Generator)
- A tool that easily allows a developer to wrap C/C++ functions for use with scripting languages. Currently supports Python, Perl, and Tcl.
- http://www.swig.org/

F2PY
- A Fortran to Python Interface Generator. [Open Source, LGPL]
- http://cens.ioc.ee/projects/f2py2e/