SAFMQ: Store and Forward Message Queue, message oriented middleware. Uses include Assured Async Messaging, SOA, Delayed/Batch, and Cluster/Grid Computing. The SAFMQ server provides cross platform communication among C++, PHP, Java, and .NET clients.
Ex-Crawler is divided into 3 subprojects (Crawler Daemon, distributed gui Client, (web) search engine) which together provide a flexible and powerful search engine supporting distributed computing. More informations: http://ex-crawler.sourceforge.net
A mobile agent framework. Instead of relying on protocols across the wire, send an agent to the server to execute.
An example is encryption: send an agent to retrieve data, but let it do the encryption. Client side encryption on the server!