Early English Books Online (EEBO) contains digital facsimile page images of virtually every work printed in England, Ireland, Scotland, Wales and British North America and works in English printed elsewhere from 1473-1700. It contains more than 130,000 titles and more than 17 million scanned pages as listed in 4 collections - Pollard & Redgrave's Short-Title Catalogue (1475-1640) and Wing's Short-Title Catalogue (1641-1700) and their revised editions, as well as the Thomason Tracts (1640-1661) collection and the Early English Books Tract Supplement.
An excellent guide to using EEBO has been created by the University of Reading and we'd recommend you'd read that along with the EEBO help pages to assist you with getting the most out of the site. A very detailed guide to features can be downloaded below.
Past Masters is a collection of full-text humanities works in scholarly editions. It contains the works and/or correspondence of many major literary authors, philosophers and other intellectuals as well as collections of correspondence by period.
Empire Online is a collection of original documents relating to Empire Studies, sourced from libraries and archives around the world. The documents are grouped into five sections: Cultural Contacts, 1492-1969; Empire Writing and the Literature of Empire; the Visible Empire; Religion & Empire; Race, Class, Imperialism and Colonialism, 1607-2007.
LION provides access to the full text of more than 350,000 British and American original works (as well as links to useful background material) and critical works such as journal articles and citations.