In 1991 there was a Saturday Night Live special featuring some of the best commercial parodies the show has made over the years. It was exceptionally enjoyable and I recommend it strongly. In 2005, a new special was created, though it tended to focus a lot more on the newer ads made by the less funny new cast (hey, I call it like I see it). Despite the show taking a nosedive qualitatively over the years, the new content is generally exceptional--though the commercials occasionally were a bit too graphic for some audiences and they tended to be a bit disgusting at times (such as talking about menstruation). Also, I have no idea why the producers insisted on including a rather annoying narration and new content featuring Will Farrell instead of just giving us a few more parodies. His intermittent bits just aren't funny and tend to disrupt the flow of the show. My advice is just try to look beyond this and ignore or fast-forward through these segments so you can see the great and super-funny segments.
FYI--On the DVD in the "Extras" category are about eight more commercial parodies.