You may not be aware, but nearly all OCW courses can be downloaded to your computer for easy offline access. Just look for the “Download course materials” link in the left hand navigation of the course.
This will give you a zip file that will decompress to a set of files replicating the entire course content locally. Look for the START.htm file in the course folder, which should open the course in a browser just like you were on the live site.
If the course has video, the video files aren’t included in the zip file (they are too big), but you can download those separately from iTunesU or the Internet Archive.