CLIO
Columbia's online catalog for books, journals, films and music.
WorldCat
Search for books and journals in major library collections around the world.
Borrow Direct
A borrowing service offered by a consortium of university libraries that includes Columbia, Brown, Cornell, Dartmouth, Pennsylvania, Princeton, Yale, Harvard, MIT, and others. Allows students, faculty and staff to request (and receive in four days) books from each other's collections.