Fedora
Fedora (or Flexible Extensible Digital Object Repository Architecture) is a modular architecture built on the principle that interoperability and extensibility is best achieved by the integration of data, interfaces, and mechanisms (i.e. executable programs) as clearly defined modules.

Fedora is a digital asset management (DAM) architecture, upon which many types of digital library, institutional repositories, digital archives, and digital libraries systems are built.

Fedora is the underlying architecture for a digital repository, and is not a complete management, indexing, discovery, and delivery application.

It is Java-based so potentially applicable to any platform.  

Read the news article about the DSpace and Fedora Themed week online session (including links to the recording of the session and the Q&A wiki).