Moscrack is a WPA cracker for use on clusters. It supports MOSIX, SSH, and RSH connectivity and works by reading a word list from STDIN or a file, breaking it into chunks, and passing those chunks off to separate processes that run in parallel. The parallel processes are then executed on different nodes in your cluster. All results are checked and recorded on your master node. Logging and error handling are taken care of. It is capable of running reliably for long periods of time, without the risk of losing data or having to restart. Moscrack uses aircrack-ng by default. Pyrit for WPA cracking and Dehasher for Unix password hashes are supported via plugins.
slkvm is an application to provide some system tools to work with clustering and virtualization. It focuses on depending on as few external tools as possible but to also support as many virtualization technologies as possible. It works in a cluster environment where heartbeat runs virtual machines of nodes that have failed. It builds an "unheaded" cluster to avoid having a clear point of failure. It is able to build a two node cluster with everything redundant. It avoids compiling a new kernel or newer version of applications, so you can benefit from Debian security updates.