You can gain a quality, fundamental understanding of mechanical engineering from the MIT OpenCourseware website. Here you can find all the undergraduate level mechanical engineering materials, easily accessible and also free of charge.
MIT OpenCourseWare is a large-scale, Web-based publication of MIT course materials. It features all the MIT undergraduate and graduate level course work. As of October 2012, over 2180 courses were available through the MITOpenCourseWare website, so if you want to learn about other topics or exploring other courses, there are a tremendous amount of options available. Examples of Mechanical Engineering courses featured on the website include Mechanics and Materials, Fluid Dynamics, Principles of Naval Architecture and Engineering dynamics.
MIT launched the website in 2002, and at the time, the university only offered 32 courses. By September of 2003, the website had over 500 courses available online. It has continued to grow rapidly, with MIT adding hundreds of free courses per year to the site. Furthermore, as of October of 2012, over 60 courses had complete video lectures. These video lectures make it easier for prospective students who prefer to watch and listen as a professor gives his lecture, as opposed to reading a transcript of that lecture.