Google Play Books - Google Play Books lets you search, preview, and buy millions of books using Google Book Search.
HTTrack - HTTrack is a free (GPL, libre/free software) and easy-to-use offline browser utility.
Amazon Kindle - Amazon Kindle software lets you read ebooks on your Kindle, iPhone, iPad, PC, Mac, BlackBerry, and...
GNU Wget - GNU Wget is a free software package for retrieving files using HTTP(S) and FTP, the most...
LibriVox - free public domain audiobooks
SiteSucker - SiteSucker is a Macintosh application that automatically downloads Web sites from the Internet.