I would like to point out that while ripping DVDs is not illegal, defeating the copy protection on commercially produced DVDs is illegal due to the Digital Millennium Copyright Act. From the Wikipedia page:

Anti-circumvention exemptions
Motion pictures on DVDs that are lawfully made and acquired and that are protected by the Content Scrambling System when circumvention is accomplished solely in order to accomplish the incorporation of short portions of motion pictures into new works for the purpose of criticism or comment, and where the person engaging in circumvention believes and has reasonable grounds for believing that circumvention is necessary to fulfill the purpose of the use in the following instances:
Educational uses by college and university professors and by college and university film and media studies students;
Documentary filmmaking;
Noncommercial videos. (A new exemption in 2010, similar to a previous educational exemption.)