Do NOT buy a DVD burner right now. Last time I saw, a true DVD burner (not a DVD-RAM) is well over $2000 and availible only in Japan. On top of that, DVD-R discs are about $30 a pop. DVD burning is not practical right now. The thing is, after the huge popularity of CD burners, companies are scrambling to put together a good DVD burner for home use. I think you will start to see the first generation of semi afforable ($500 or less range) DVD burners in about two years.
If you want to copy DVD movies, look in to divx(mpeg4) ripping. tomshardware.com has a quick overview about it on their site. A couple of programs and a DVD-ROM, and you can burn DVDs to CDs with decent quality. Can only watch em on a PC though.