The Three Act Structure

Well the best film I know for a three-act structure is the movie Inglourious Basterds. Admittedly the acts are pretty much spelled out for the viewer, but I still think it's a good example to use. Ironically Professor Ramirez-Berg pointed out Tarantino as using a lot of alternative plotting in other movies in his article.
While keeping spoilers to minimum, I will try to explain the acts and the events in them. The first act is the standard story setup. A girl's family is killed by the SS and their commander, and the Basterds are formed setting up both groups of protagonists. It also sets up beginning of the conflict that the main characters have. The climax of the act is when the Nazis plan to have a film premiere in the theater owned by the girl with the murdered family. Because of this, she now can take her revenge.
The second has the complications. The girl decides to implement a plan to assassinate the Nazis on her own. The Basterds learn of the premiere and want to kill the Nazis themselves. Their plans go awry in a shootout, but they decide to continue because of who is attending the movie, escalating the stakes. This decision  is the climax of the act.
The final act is the climax of not just the movie, but of the twin assassination plans. Two of the Basterds, including their leader, are captured by the SS commander while the rest of the team put their plan into action. The girl's plan also works and together the two groups kill all the Nazis in the theater. However, the climax of the movie, and act happens later, when the leader of the Basterds makes a deal with the SS commander to escape with him.