Tracking shots, or "long takes", are among the most difficult things to pull off well in a film. That's why top-rank directors are so enamored of them. It's the ultimate cinematic showoff. Everyone agrees that the best example of the technique was the opening of Orson Welles, "Touch of Evil", but what are the other bests? I posted on a list of the best here which included some impressive work. Now I refer you to another list assembled by FilmCritic.com [here]. It starts, of course, with Welles, and does not completely overlap the previous list.
To whet your appetite, here's the famous opening sequence from "Touch of Evil" -- yes, that is Charleton Heston playing a Mexican cop and Janet Leigh as his bride. Note how Welles toys with the viewer. Note also, this was filmed before the invention of the steadicam -- they were using cameras that, fully blimped, weighed 500 pounds.
