Howdy, folks! John K. has a bunch of old commercials posted on his blog that he and his studio Spumco created a few years back. Watch them here. They are all mini-quicktime downloads, which is fun because you can step through them to look at specific keyframes. The Old Navy ones in particular are real gems. I remember them being on TV, as well as the old Nike spot. He notes that his main goal was to make commercials you wouldn't want to fast forward through.
When you watch them, note a number of things. The timing (music, animation, sound effects, pacing) is nearly perfect. The animation is extremely fun to watch (a lot of great drawings went into these). The character design is amazing. And lastly, but probably most importantly, look at the variety of color schemes! The backgrounds aren't entirely naturalistic, and in some of them, even the sky changes color from shot to shot.