Students at the University of Pennsylvania have on-site borrowing privileges at the following schools: Brown University, Columbia University, Cornell University, Dartmouth College, Duke University, Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Princeton University, Stanford University, University of Chicago and Yale University. There are restrictions that vary by university. For example, the Stanford University Graduate School of Business Library is not included in BorrowDirect Plus On-Site Borrowing privileges. For details see the Borrow Direct Plus On-Site Borrowing site with links to each university's policies.
You can search the collections of these universities through the BorrowDirect catalog.