The overall objective of the XtreemOS project is the design, implementation, evaluation, and distribution of a grid operating system (called XtreemOS) with native support for virtual organizations (VO). XtreemOS is capable of running on a wide range of underlying platforms, from clusters to mobiles. It is based on Mandriva Linux, with support to come for other distributions later.
Java distributed framework is a framework for distributed grid and / or volunteer computing. It's divided into a server and client library. You can create new or implement it into existing applications in no time; you don't need knowledge about network connections, sockets, etc. The Framework does almost everything automatically. It provides secure automatic client <-> server communications, unique IDs, automatic resending of jobs to new clients if needed, user stats, and much more. The client framework supports the detection of the computer's user state (idling, away, online, etc.). It also offers many other useful features and helpers for developing a distributed client application.
Makeflow is a workflow engine for executing large complex applications on clusters, clouds, and grids. It can be used to drive several different distributed computing systems, including Condor, SGE, and the included Work Queue system. It does not require a distributed filesystem, so you can use it to harness whatever collection of machines you have available. It is typically used for scaling up data-intensive scientific applications to hundreds or thousands of cores.