Concordion is an open source tool for writing automated acceptance tests in Java. There are also versions for .NET, Python, and Ruby.
Web Site: http://www.concordion.org/
License and Pricing: Open Source, Apache License, v2.0
* Why I prefer Concordion to FitNesse
* Writing Stupid Specifications with Concordion
* Concordion vs. Cucumber and Java based Acceptance Testing
* ATDD Acceptance Testing using Concordion
* Automated Acceptance Tests and Requirements Traceability