I assume you mean purchased Hollywood movie type DVDs right? If so, then technically the is no legal way at all. It isn't the copying of the material that is necessarily illegal (doing so may fall under fair use depending on your purpose). The problem is the breaking of the copy protection built into those DVD is what is illegal due to the Digital Millennium Copyright Act (DMCA).
This law may be changed in the near future as there have been attempts and will continue to be to loosen this to protect certain consumer rights, but as of right now, circumventing the built in copy protection of a Hollywood DVD is illegal. So even if under fair use you could make a copy to your iPod or a VCR tape, to get to that point, you have to violate the Digital Millennium Copyright Act.
Patrick