One of the things the folks from the Smithsonian that I talked to wanted was a web service that would resolve journal abbreviations. Actually, what I think they really want is a service that can take in a cryptic citation and output a nicely formatted one with the full journal title, etc. There are lots of web sites that list various journal abbreviations, and even All That JAS which is a bibliography of those sites, but in my limited looking around I didn't find anything that quite does what they want, even for just the journal abbreviations.
I imagine that many OpenURL resolvers try to cope with journal abbreviations, and a citation-expander would fit easily into the OpenURL 1.0 framework, but I'm not aware of one. Not having a handy list of journal abbreviations, I thought it would be interesting to see what could be gleaned from WorldCat.