Here are some links for ripping DVDs for Mac and PC from the Chronicle of Higher Ed and TechHive.
To record online video, we used to use Camtasia or other screen capture software, but now programs like Quicktime for Mac contain screen capture functions. In Quicktime, it's as simple as File>NewScreenRecording, but there's one trick--getting sound. I installed a free soundcard called "Soundflower" which allows sound to pass between programs. Once installed, you go to SystemPreferences>Sound, choose the "Output" tab and choose "Soundflower Ch2." Go back to Quicktime and in the NewScreenRecording record button window, click the triangle on the right for a dropdown menu, and select "Soundflower Ch2." Then, click the red button to start the recording (you can also drag the cursor to select a part of your screen to record). Hit play on the video you want record, and click the Quicktime button again to stop the recording. Finally, export the video file to your desktop [File>Export...] in the format you prefer. NOTE: Mac OS 8 apparently a Gatekeeper application that has revoked Soundflower's certificate; so installation is no longer recommended for OS 8 and above. Please share your methods for ripping video, legally, for media literacy education, in the comments below.
Also, if you practice outside the U.S., let us know about the legality of ripping video for teachers in your country.