Google Books service has so far converted thousands of books into a readable format. Although this is mired in controversy, I'm glad someone is doing it. Furthermore, the software that converts the text is very smart (even able to convert ancient greek!) and now available for public use (Google Docs account required).
Unfortunately, initial reviews of this service have not been kind. Hopefully it gets better.
Google is not the first to market on this one as there are many other services for optical character recognition (OCR). The difference will likely be that Google will likely let users upload larger documents for conversion as a feature of its competition with Microsoft Office (which has no such capability).