Reciprocal Borrowing Program for Northwestern students and faculty at the University of Chicago, University of Illinois at Chicago, and Loyola University.
Worldcat contains over 95 million records from the online catalogs of libraries around the world, but particularly in North America.
Hollis Harvard's Online Catalog
Karlsruher virtueller Katalog allows cross-searching of many German and other international library catalogs.
I'm regularly available in the Philosophy Department's Brentano Library (Kresge 3520) from 12:00 - 1:00 on Mondays, and in the Classics Seminar Room (Kresge 4364) from 4:00 to 5:00 on Tuesdays. I'm also always happy to meet in my office in the library by appointment: just click on the link above.