Stackless has been applied in a commercial context by:

• EVE Online from CCP Games

  "When embarking on the creation of EVE Online, a single shared persistent world we realized two things: We could not given constraints of time and commercial reality do this in a compiled language and we needed innovative concurrency control for such a large scale shared state simulation across tens of thousands of CPUs (EVE Clients included). After many experiments with various combination of existing scripting languages and NT fibers we arrived at Stackless Python. Stackless Python offered us the power of Python coupled with a vastly superior concurrency control mechanism over anything we had seen before, first as continuations and later with an innovative channel based API. CCP's commercial success today is built on the single decision of selecting Stackless Python as our foundation." -- Hilmar Veigar Petursson, CEO of CCP Games.

  There is a talk from Kristján Valur Jónsson: Stackless Python in EVE .

• Sylphis3D

  A 3D game engine with design around the concepts of Stackless Python. Stackless is used as more than a scripting language. Most of the engine (except the renderer and physics simulation) is coded in Stackless Python, making heavy use of tasklets to create a very dynamic, easy to follow and powerful gameplay definition framework.

• JP Morgan's Athena (PDF link).

  Athena is J.P. Morgan's cross-market risk management and trading system. It is currently used in their foreign exchange and commodities businesses, and is being rolled out more broadly across our fixed income businesses. Athena includes a globally replicated object-oriented database, a powerful dependency graph and a fully integrated stack across pricing, risk and trading tools. Athena is designed to pull developers close to the business to help increase revenues while improving operational processes and controls to reduce costs. Athena's main development language is a derivative of stackless.

• flowGuide from science + computing ag

  A continuation based workflow management system, that makes it possible to write a distributed workflow as if it was running on a single computer.

Known non-commercial applications are:

• Nagare: A continuation-based web framework which makes it possible to code a web application like a desktop application, with no need to split its control flow in a multitude of controllers and with the automatic handling of the back, fork and refresh actions from the browser.
• A population simulation in Stackless: Written by Boudewijn Rempt, you can also read about it in this article on informit.com.
• PYXVR: Uses Stackless in a simulation example.
• Hobocat: A 2d action/puzzle game