Gutenberg.org
Gutenberg.org is one of the most famous sources for free ePub eBooks. They offer about 30,000 books in many different languages.
Website language: English
Manybooks.net
Manybooks.net offers more than 26,000 free eBooks in many different languages. Definitely a place to go when you are searching for free eBooks.
Website language: English
Mobileread.com
Mobileread.com offers more than 1,800 free ePub eBooks. Most of them are English but there are also many in German. The Mobileread.com community is very active, so there are added several new books almost every day.
Website language: English
Mendele.co.il
Mendele.co.il is the first website which offers ePub eBooks in Hebrew.
Website language: Hebrew