I just finished learning about copy cataloguing. This is a process I have been doing for a number of years but never knew it had an official term. This is the act of getting MARC records from sources such as Canada's AMICUS and the Library of Congress. I do find the AMICUS interface and quirkiness a bit off putting but will use it more often just the same.
What I have not been doing very much, is increasing the quality of these records by adding to the summary or adding to a myriad of other 5xx tags. I can be using my Sears subject headings handbook and be adding heading that would be useful to my patrons. I also realize that I can add summary information from a number of existing items I have that would be very useful to helping teachers identify curricular links.
I found another very valuable resource through our course materials and that is World Cat. I found I could even pay a subscription fee based on how many MARC records I would likely need to download in a year. World Cat is kind a cataloguing coop where member organizations share their records. A very neat feature of World Cat is the free world catalogue search that is available. You can search a collection of nearly 1.5 billion books world wide and locate a copy in a member library closest to you. All you have to do is put in your postal code.