General Online Book Collections:
Libraries' Catalog--searches for ebooks in the UA Libraries' databases and ebook packages, including Sabin Americana, Early English Books Online, Eighteenth Century Collections Online, and more. Before searching, select "Electronic Resources" from the "Limit To" box to limit your search to ebooks.
Google Books--find citations to thousands of online books. Some charge a fee, but others are fully available online for free.
HathiTrust--a group of over 50 libraries offer this ebook collection.
Internet Archive--increasingly one of the best sources of ebooks.
***Google's main search page searches some, but not all, of the contents of Google Books, Hathi, and Internet Archive