Yahoo's Open Content Alliance and Google Print seems to be promising and would be considered popular resources for online books. However, this effort of indexing and digitizing books and made freely downloadable online has already been spearheaded a long time ago and has indexed and digitized 16,000 public domain books. It's called Project Gutenberg. It has been doing what Google and Yahoo aims to do for a long time already. The only problem is that they are not as famous as the other two search engines mentioned. So the Project may be facing a problem. A popularity, and maybe financial, problem. So will they sink or swim? Well, everything sinks in the end. It's just a matter of time. I just hope they sink gracefully. Go visit Project Gutenberg and broaden your mind.