Open Library is the online catalogue project of the Internet Archive. It has been gathering catalogue records from world’s biggest libraries since 2007. Currently there are over 20 million edition records online and access to 1.7 million scanned versions of books.

HathiTrust Digital Library is a repository of digital material from 50+ research libraries plus content from Google Books and the Internet Archive. Hathi is the Hindi word for elephant, an animal famed for its long-term memory. There are 9.7+ million volumes with 2.6 million in the public domain. There is full-text searching across the entire repository. A free Friend Account allows you to create your own collections which can be set to public or private.
Tip: You can search just within your own collections for the full-text of items.

Sites with collections online
Ask about Ireland is an initiative of Irish public libraries, local museums and archives to digitise and publish online original, unusual and unique material from their local studies' collections. Use the Reading Room link to access a vast collection of unique digital books. The collection is arranged by county and subject (church history, history of Ireland, geography of Ireland, Irish people and many more). Books can be viewed online. 
 
Library Ireland is a free online resource of books and articles on Irish history, genealogy, and culture. The transcripts of a wide range of journal articles, old books, including directories, are available online with full text searching. You can browse the categories which include genealogy, Irish names, history, social history, folklore, music, people and places.

British History Online is a digital library containing some of the core printed primary and secondary sources for the medieval and modern history of the British Isles.
 
Family History Archive is a digitised collection of published genealogy and family history books and periodicals held by the Family History Library, Salt Lake City, Utah and other participating libraries. This ongoing project currently has 17,777+ items online including histories of families, county and local histories, how-to books on genealogy, genealogy magazines and periodicals, medieval books (including histories and pedigrees) and gazetteers. You can also use the Books link on the main FamilySearch page for access.

Titles in the Family History Archive are also linked to the FamilySearch library catalog. The catalog offers place-names, last names, keywords, titles and other searches from the drop down menu box.  Search returns can be filtered by various categories.

Tip: Use the Availability filter and choose Digital Images. Any records listed here can be viewed online for free by clicking on the record and then selecting the View this publication online option.

Searching for resources
WorldCat is a global catalog of library collections. You can search for books, DVDs, CDs and articles from the collections of 10,000 libraries worldwide. Currently over 1.5 billion items are listed.
Tip: Do a phrase search for your family name + family – “Smith family” to locate published family histories.

Trove is the National Library of Australia’s enhanced search service that aggregates the information from 1000 libraries, art galleries, archives and museums in Australia. Over 90 million items are available. It offers combined or individual searches of digitised newspapers; journals, articles and data sets; books; pictures, photos and objects; music sound and video; maps; diaries, letters and archives, archived websites (1996 to present); people and organisations plus lists (created by other users of Trove).
Tip: To locate online material – Use Refine your results – Availablility – Online. Items held by the Open Library, Hathi Trust and others are identified and linked.

GovPubs. The Australian Government Publications Guide to publications, such as Acts, Hansards, Gazettes and Parliamentary Papers, located in Australian libraries or available on the Internet.