Best Buy & Circuit City - check the ads every week because new movies are sometimes cheaper one place or the other you really have to look. Also check
www.deepdiscountdvd.com, www.dvdplanet.com (great critereon prices!), and for the hard to find ones EBay but beware of the evil bootleggers. Oh and by the way deepdiscountdvd has over 400 DVDs buy 2 get 1 free.