All of the featured Open CourseWare items contain open educational resources and all of them have the general aim of sharing content to a wide audience. The things that I think matters that differ between them are the more specific intended audience, whether the courses are offered with actual credit, the quality of the courses, and the modularity of the content.
Open University (UK) Open Content Initiative
Open University contains courses that range in many different subject areas including language, technology and philosophy. The courses are college level and each course ranges in time from 5 hours to 40 hours or more. The Open University Open Content Initiative can lead to actual college credit hours and offers media that is mainly text and graphics. The audience is limited to college level students.
Rice offers many college level courses but is not restricted to these. Connexions sees its users as re-sharers of courses and as collaborators on the effectiveness of the same. This is evidenced by the fact that they allow users to comment on content and share their own if they want. Most of the content is text and picture based. Connexions does not organize its content into linear lessons but tries to provide content piece by piece. This modularity seems to add to the idea of allowing easy remix of content but makes Connexions difficult to navigate in my opinion.
Carnegie Mellon Open Learning Initiative
Carnegie Mellon offers a much smaller number of courses but increases the instructional quality of their courses. They take user data and use it for formative evaluation processes. The courses on Carnegie Mellon can be taken for college credit or not. The audience is college level but can also extend to other life-long learners. the courses feature instructional tools such as cognitive tutors, virtual laboratories, group experiments and simulations.
UNESCO Open Training Platform
UNESCO caters to a more worldwide audience featuring instructional materials that are not from college classes, but are more focused on social and economic issues. The resources often had a third-world use and were more localized than the other open education projects. UNESCO's site includes many different ways of exporting content, and a variety of media formats.
MIT was the largest of the open education projects with over 3000 courses. The courses are meant for the specific audience of college level students. MIT OCW is made up of content that is mostly in a non-remixable format, pdf, but there are also some text classes and videos. The courses are very linear and they allow for downloading of an entire course.
National Repository of Online Courses
The National Repository of Online Courses offers a limited number of college and high school level open courses. They evaluate the quality of their courses using user evaluations, and other important tools. The media that they use is generally more sophisticated than the other sites. It involves pictures text and audio in a type of slideshow presentation on each topic. This makes and enjoyable experience for the learner, but does not readily allow for remix of the media.
I am not sure what quality means to those who work on the open education projects listed above. There are many ways to think of quality in Open CourseWare. For some, quality probably means accessibility. Quality could mean accuracy or remixability of content. Quality could mean a high amount of content. Quality could mean giving the users the ability to comment on content to help make it better. I prefer the methods that the Carnegie Mellon Open Learning Initiative and the National Repository of Online Courses use to evaluate the quality of their content. Both of these projects report that they gain feedback from the user to improve their courses. The Carnegie Mellon Open Learning Initiative also takes user performance data to determine where instruction is lacking and where they can add remediation. Instructional effectiveness should be considered as a quality measurement too.