EDINA is doing some great work with their Join-Up project, bringing together:
1. Table of contents alerting (ZETOC)
2. Document discovery/database searching (Xgrain)
3. OpenURL-compliant linking brokerage (ZBLSA)
4. Document delivery (DOCUSEND)
They've also put together a presentation of the advantages of a centralised broker for locating journal articles.
Another demonstration of the power of OpenURL resolvers is provided by UKOLN.
As a result, links to ZBLSA are now incorporated into HubMed search results (example link).