From Radar O’Reilly:

Greenplum – Scott Yara. At the heart of most web 2.0 applications is the management of big data. Greenplum’s massively parallel Postgres database is the highest performance open source database around.

Hyperic – Javier Soltero. If operations is advantage, Hyperic would like to help more companies find that advantage. They’re also building a Web 2.0 ecosystem in which the software gets smarter the more people use it.

Django: Adrian Holovaty. Like Rails, Django is a case where the application was kept proprietary, but the framework used to build it was released to the world. Is this the new model for how to open source a web application?

DabbleDB – Avi Bryant. OK. This thing is built with smalltalk. What else do you need to know? It’s a web-based database, potentially asymmetric competition for Access and Filemaker, but it’s also a data multiplexer that can help to give people more control over their own data.

Alfresco – Matt Asay. There are a lot of open source content management systems, but Alfresco is the one that’s targeted where the money is, and that has built the robust data store to meet the needs of big companies.