http://csrc.nist.gov/groups/SNS/acts/documents/comparison-report.html

It can compute tests for 2-way through 6-way interactions.  An easy-to-use GUI is included, in addition to a command line version suitable for use in scripts or system calls from another tool.  A comparison of ACTS with similar tools shows that ACTS produces smaller test sets (with the same degree of coverage) and is faster than others.  ACTS is Java-based, so it will run on any Java platform. 

http://csrc.nist.gov/groups/SNS/acts/images/acts_defn.jpg