I am also not aware of such websites since good OO design is difficult to measure and the major impact is on quality and non-functional aspects of the system (m

I am also not aware of such websites since good OO design is difficult to measure and the major impact is on quality and non-functional aspects of the system (maintainability, reusability, testability etc). In addition to the books mentioned in above link I'd like to wholeheartedly recommend Domain Driven Design by Eric Evans. I've found the described approach very helpful in design of enterprise applications on the Java platform.