Avaki is focused solely on the enterprise model. Specializes in life sciences, engineering/manufacturing, financial services. Claims to be platform independent. Note: Now part of Sybase.
Data Synapse is focused solely on the enterprise model, and specializes in financial services, energy and data mining. Uses a Java platform, but provides a C++ programmer's interface.
Entropia is focused solely on the enterprise model. Specializes in pharmaceutical, chemical, materials science, financial services, engineering, and energy. Windows-based. Note: Entropia reportedly ceased commercial operations in 2004.
IBM
Parabon is focused on enterprise sales, but is also pursuing the public exchange model. Specializes in bioinformatics and financial modeling. Java-based.
Platform Computing is focused solely on the enterprise model. Specializes in life sciences, manufacturing, government/research and financial services. Platform software is hardware-agnostic and integrates with and supports all major operating systems, including UNIX, Windows and Linux, to effectively manage and optimize heterogeneous distributed computing resources.
Sun Microsystems
Univa UD is focused on the enterprise model, but has hosted several Internet public exchange modeled projects to demonstrate security and scalability. Specializes in pharmaceutical, chemical, materials science, industrial design and geosciences.