Beta 1 of the Windows Compute Cluster Solution was annouced today - www.microsoft.com/hpc. You can nominate yourself for the beta at - http://www.microsoft.com/windowsserver2003/hpc/beta.mspx
This will be very useful to the scientific apps that had been trying to use BizTalk to handle some of the scientific computing workflows. I'm quite interested in seeing apps that try it out - I'm sure Paul Roe from QUT will be moving their Bioinformatics project over to it. http://msdn.microsoft.com/workflow has all the info - including hands on labs and Try out Windows Workflow Foundation online at MSDN VirtualLab.