The new WorldCat Basic API worldcat.org/devnet/wiki/BasicAPIDetails provides an easy method to search WorldCat
Anyone can gain access to the WorldCat Basic API for non-commercial purposes from the WorldCat Affiliates site www.worldcat.org/wcpa/content/affiliate/, by signing up for a unique key to use the service. Commercial uses of the WorldCat Basic API are encouraged, but interested parties are required to contact the WorldCat Partnership team to arrange access.
OCLC Web Services offers ways to connect people to knowledge through libraries, and for libraries to reap the benefits of library cooperation.
There are many other Web Services www.oclc.org/services/web available from OCLC, including the more full-featured WorldCat Search API, and also ready-made WorldCat widgets www.worldcat.org/wcpa/content/affiliate available for download.
Feedback about any of the OCLC Web Services is welcome on the OCLC Developer Network blog and mailing list, available from the OCLC Developer Network site