The Virtual International Authority File (VIAF) is a project jointly administered by LC, the BnF, the DNB and OCLC. The National Library of Sweden is also a participant, soon to be joined by several other libraries. We currently have about 7.8 million VIAF records built from 9.2 million source records.
The VIAF site has recently had a major overhaul. What you now search are records created from a merge of matching source authority records. Within this record you can see what source records were used to create it, along with cross references and other information gleaned both from the authority records and from associated bibliographic records.
In addition to the VIAF record there are MARC-21 and UNIMARC views of the data. For example, here is the record for Barbara Tillett (one of the main forces behind VIAF) : http://viaf.org/viaf/77390479. By adding a file extension you can get a MARC-21 version: http://viaf.org/viaf/77390479.m21, and a UNIMARC view: http://viaf.org/viaf/77390479.unimarc. The MARC export is new, so any error reports are welcome.
In the not too distant future we expect to offer a 'linked data' view of VIAF.
We know we have work to do to refine the matching process, but are interested in errors people notice, both names that should have been brought together and those that should not have, as well as interface problems you may have.