Eric is right, a few European institutions have been doing this for 
several years. At the University of Bath we've been using ELIN 
http://elin.lub.lu.se/elinInfo, which Lund University in Sweden had been 
operating since 2001 (until recently - it's now been effectively spun 
off.) This is also what underlies the DOAJ site http://www.doaj.org/

It seems to me that there are two approaches to building these 
aggregated indexes:
  (1) load whole databases (mostly A&I) and catalogues, as an 
alternative to federated search, and
  (2) collect article-level metadata, mostly from primary publishers, to 
build an index of the library's e-journals collection, then possibly add 
the "print catalogue."

LANL sounds like it's taken the first approach; ELIN and Journal TOCs 
http://www.journaltocs.hw.ac.uk/ are based on the second. The approach 
taken by the commercial vendors is somewhat blurred between the two, but 
I would suggest that EBSCO Discovery Service and OCLC WorldCat Local are 
broadly based on the first approach and Serials Solutions Summon and Ex 
Libris Primo Central are more focussed on the second. I think this is an 
important consideration for anyone selecting a service, or contemplating 
building their own.

Laurence Lockton
University of Bath
UK