OCLC Classify : Tool to find Classification numbers (DDC) and subject headings

OCLC Classify prototype is designed to help users apply classification numbers.

Classify provides a user interface and a machine service for assigning classification numbers and subject headings. The database is searchable by many of the standard numbers associated with books, magazines, journals, and music and video recordings. These numbers include:

ISBN (International Standard Book Number)
ISSN (International Standard Serial Number)
UPC (Universal Product Code).

The database is also indexed by OCLC record number, title and/or author and FAST headings.

For more details : http://classify.oclc.org/classify2/