xISBN is now being joined by xISSN, a new Web service. With this service you can supply an ISSN, and find out about any predecessor, successor, and alternate ISSNs and titles, and find the electronic ISSN for a print title or vice versa.
This is a web service which can be integrated into library applications, websites, link resolvers, cataloging tools, and so on. There is also a pretty nifty human-ready demonstration interface known as Title History.
(Lorcan Demsey's weblog)