As of May 20th, Rogue Wave halted development of Ruple, a Java-based fusion of XML and TupleSpaces.  XML TupleSpaces is a nice idea, but difficult to sell.  If you are interested in TupleSpaces, here is a paper you might enjoy: Dynamic PKI and Secure Tuplespaces for Distributed Coalitions.

I am getting a dangerous itch to apply tuplespaces to web services workflow problems.  TupleSpaces are extremely powerful as coordination infrastures so tuplespaces and web services go very well together IMHO.