Production ready Python implementations besides CPython?

Except for CPython, which other Python implementations are currently usable for production systems?

The questions

What are the pros and cons of the various Python implementations?
I have been trying to wrap my head around the PyPy project. So, fast-foward 5-10 years in the future what will PyPy have to offer over CPython, Jython, and IronPython? and
Migrating from CPython to Jython

already shed some light on the pros/cons on the topic. I am wondering now, if those more exotic implementations are actually used in systems that have to run reliably. (possible examples? open-source?)

EDIT: I'm asking for code that needs the Python version >= 2.5

Solution

CPython

Used in many, many products and production systems

Jython

I am aware of production systems and products (a transactional integration engine) based on Jython. In the latter case the product has been on the market since the early 2000's. Jython is a bit stagnant (although it seems to have picked up a bit lately) but it is mature and stable.

IronPython

This is the new kid on the block, although it does have some track record in products. It (particularly version 1.x) can be viewed as stable and ready for production use, and development is officially funded by Microsoft, who appear to have an interest in dynamic languages on top of the CLR. It is the greenest of the major python implementations, but appears to be reasonably stable.

Stackless Python

This is used extensively in EVE Online, and they seem to view it as production ready. Bear in mind that Stackless Python has been around for something like 10 years.