As I've mentioned in DSpace and DOOR ticket (please, forgive me for being repetitive):
DSpace and Fedora supports OAI-PMH protocol:
See http://en.wikipedia.org/wiki/Open_Archives_Initiative_Protocol_for_Metadata_Harvesting
And also Registry of Open Access Repositories (ROAR) http://roar.eprints.org/index.php
List of repositories supporting OAI-PMH:
Fedora
GNU EPrints from the University of Southampton,
Open Journal Systems from the Public Knowledge Project,
Desire2Learn,
DSpace from MIT,
HyperJournal from the University of Pisa,
Primo,
DigiTool,
Rosetta
MetaLib from Ex Libris,
DOOR from the eLab in Lugano, Switzerland,
panFMP from the PANGAEA (data library),
jOAI
It will be also interesting implement a client for SQI Protocol (i.e Merlot and Ariadne):
See:
http://ariadne.cs.kuleuven.be/SqiInterop/free/SQIImplementationsRegistry.jsp
Possible?