Local

Boston Library Consortium (BLC)
Academic & research libraries in the greater Boston area & New England, including Wellesley College. Get a BLC card by contacting a subject specialist librarian and borrow directly from any of these libraries.
MIT Libraries
Your Wellesley ID gives you borrowing privileges at MIT libraries - you don't have to be cross-registered at MIT. See the "Guide to MIT libraries," available at any MIT library. If you're cross-registered , you can also get an MIT ID card at their Student Center.
Harvard University Libraries & Museums
Access policies vary. Wellesley College students and faculty have access and limited borrowing privileges at several Harvard libraries - please consult a Research & Instruction librarian for more information. Faculty may apply for a Widener Library Grant (see Letter E.) through the Dean of the College's office.
Minuteman Library Network (MLN)
A consortium of public and small college libraries in the Metrowest area surrounding Wellesley. Get a Minuteman library card at Wellesley Free Library with proof of Wellesley residency and borrow books & videos at any of the 41 Minuteman libraries.
Fenway Library Consortium (FLC)
A cooperating group of libraries in Boston's Fenway area.
Boston Public Library (BPL)
The Boston Public Library system includes a Central Library, twenty-four branches, a map center, a business library, and a website filled with digital content.  You can register online for an eCard to gain access to ebooks, streaming media, and databases from the BPL.  You can also obtain a physical card at any branch library with proper ID.   

Other U.S. libraries

US Academic Libraries - Libraries on the Web
Library of Congress
Over 12 million bibliographic records representing books, serials, computer files, manuscripts, cartographic materials, music, sound recordings, and visual materials from the Library's collections.
WorldCat
Search most U.S. and many foreign library catalogs at once.
To request items we don't own, click on the title for the full record, then click on the Find It!@Wellesley button.

Libraries worldwide

Libweb - Library Servers via WWW
currently lists libraries in over 125 countries worldwide.
lib-web-cats
A searchable directory of libraries throughout the world.
The European Library
A portal offering access to the combined resources of the 43 national libraries of Europe.