The Cetus Project site has
many
thousands of useful and well-organised links on O-O (over 18,000 at the
last count). There are also mirror sites in many countries on several
continents.
Amongst many other things, this includes a link to an article on the
official
Eiffel
language website, which gives a comparison of the main O-O
programming
languages.
To learn more about the book this website supports, please visit its Information Center.