Library of Congress
LOC - Understanding MARC
Resource on understanding MARC principles, as well as reference materials for most used MARC fields.
LOC - MARC Standards
Authoritative resource on everything MARC, from general information to RDA in MARC.
LOC - Cataloguing in Publication Program
Explains the process of CIP - informative for how much can be expected for a resource, and what you'll need to add.
LOC - Resources for Cataloguing
Portal site on the LOC website with over 25 links pertaining to cataloguing.
Online Computer Library Center
OCLC - About RDA
Portal site with both OCLC and non-OCLC resources on RDA. Includes overview and training resources
OCLC - Bibliographic Formats and Standards
Extremely useful reference tool to use while inputting data into MARC fields. Each field and subfield is defined, and examples are provided.
OCLC - Resources for Dewey Services
Contains the DDC Introduction, the Summaries, and updates. Also has other resources.
Association for Library Collections & Technical Services
ALCTS - Cataloguing Resources
Collection of cataloguing resources from the library community's definitive technical association.
ALCTS - Resources for Cataloguers of Children's Materials
Portal site of cataloguing resources geared specifically to librarians working in school libraries or children's/YA departments.
Miscellaneous
025.431: The Dewey Blog
Explains current and previous updates to the DDC.
RDA Toolkit: Training Resources
Portal site for various trainings on RDA.
SLJ Search: "Cataloging"
Takes you to the search results page of searching the School Library Journal for the word "cataloging".