The University of Texas at Austin's Latin American Network Information Center, or LANIC, has a section on Libraries and Reference:
The section includes a listing of links for libraries and archives in North America which focus on Latin America, as well as institutional and national libraries and archives in all the Latin American countries.
The International Federation of Library Associations and Institutions, or IFLA, features the Latin America and the Caribbean Section, which has the goal of encouraging activities related to access to information in the LAC region, and their (relatively new) blog includes posts regular updates on librarianship and IFLA-related
Americanismo lists libraries and archives (as well as museums, cultural centers, and documentation centers) in Spain which focus on Latin American topics. The libraries can be listed alphabetically by name, city, or by typology.
Bibliografía de la Literatura Española desde 1980 is a comprehensive database of works of Spanish literature published since 1980, including books, periodical articles, book reviews, bibliographies and conference proceedings. The title of the database does not seem relevant to libraries in Latin America, but using Spanish terms, and possibly relying on the index available, many resources about Latin American libraries, and Latin American library holdings are available. The text of the materials is not available through this site, however the books all seem to be available through WorldCat.