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.
My grid services colleague, Tim McCormick, provided the above detail, and also explained terms and conditions. The XML Web service is offered at no charge to OCLC members with cataloging subscriptions or to any low-volume users; and for fee to others. The Title History tool is free to everyone.