Message Passing in Java

• HPJava
• mpiJava
• MPP -- Light Weight implementation of MPI in pure java
• JMPI --Implementation of MPI in pure java using RMI
• MPI Official web site
• MPICH --An implementation of MPI
• LAM --Another implementation of MPI

Middleware for Distributed Applications

• Jini
• Apache Axis
• Check a few web services in action
• Quick Start Guide for Axis
  
• Jan New March's tutorial for Jini 

A few interesting projects, trying to integrate different middleware for Distributed Applications

• Judy --Integrating Jini and WebServices
• RMIX-- SOAP over RMI
  
• JISGA

Fault Tolerant MPI libraries

• MPICH-V MPI Implementation for Volatile resources
• FT-MPI
• The Los Alamos Message Passing Interface

Random interesting stuff

• Leslie Lamport writings