Drools-solver solves planning problems.
It has moved to trunk and the reference manual is now available at:
http://users.telenet.be/geoffrey/tmp/solver/manual/html_single/
It's still experimental though.
We even made 2 blogs about it for the price of one:
http://blog.athico.com/2007/09/drools-solver.html
http://blog.athico.com/2007/09/drools-solver-in-nutshell.html
Have fun.
--
With kind regards,
Geoffrey De Smet