Search WorldCat - WorldCat is the world's largest library catalog. It has upwards of 1.5 billion items available in libraries from around the world. Use WorldCat.org to find materials in your local library, get citations, read reviews, make lists and more.
HathiTrust is a digital repository for research libraries. Brought together are significant collections of partner institutions.
USA.gov - Find government information by topic and agency such as grants and loans, immigration and citizenship, passports and travel, health insurance and food safety, and much more.
LibraryThing Mobile App - Something fun for book lovers. The world's largest book club, you can catalog your books, find reviews and others who read the same things you do.