purl.bioontology.org - Bioinformatics community project hosted at the National Center for Biomedical Ontology.

demo.sharedname.org - Bioinformatics community project hosted at Shared Names.

purl.zepheira.com - PURL service for Zepheira and its customers.

purl.access.gpo.gov - Access to US government documents via the Government Printing Office.

purl.fcla.edu - PURL service of The Florida Center for Library Automation.

The Callimachus Project implements PURLs as of December 2012.

Don't see your PURL service here?  Please tell us!