According to GCN, NIST has released a revision to SP800-60 Vol 1 and Volume 2. The two-volume Special Publication 800-60 Revision 1, “Guide for Mapping Types of Information and Information Systems to Security Categories,” is a revision of guidelines published in 2004.
Asset and data classification is the keystone to building proper protective schemes. Simply, if you don't know what you have, you can't apply the appropriate levels of value and importance.
SP 800-60's intro reads:
"The identification of information processed on an information system is essential to the proper selection of security controls and ensuring the confidentiality, integrity, and availability of the system and its information. The National Institute of Standards and Technology (NIST) Special Publication (SP) 800-60 has been developed to assist Federal government agencies to categorize information and information systems."
Give this document a read; while it is geared to a federal agency audience, it is entirely useful for baselining your own classification process.