Library of Congress - The Library of Congress is the nation’s first established cultural institution and the largest library in the world, with millions of items including books, recordings, photographs, maps and manuscripts in its collections.
EdSITEment  high-quality material on the Internet in the subject areas of literature and language arts, foreign languages, art and culture, and history and social studies.  EDSITEment is a partnership between the National Endowment for the Humanities and the National Trust for the Humanities
Shmoop - learning resources founded by David Siminoff and his wife Ellen Siminoff was originally conceived to generate a love of learning in kids.
Shakespeare Online - visitors can read every play or poem from the world's most celebrated writer and, more importantly, make some sense of his works with free analysis, Old English language translations, and famous quotes.
Merriam Wesbter - Online Dictionary and Word Tool

 

National Geographic South America (sign up for a free account)