As the old adage goes, "The show must go on." Almost Famous concludes with a montage, set against the backdrop of Led Zeppelin's track "Tangerine"—a title Cameron Crowe actually considered for the film before finally landing on Almost Famous (source). In this sequence, we see Stillwater on stage looking happy, William with his mother and sister around the dinner table looking happy, Stillwater on the cover of the Rolling Stone looking happy, and the band bus Doris rolling along on the "No More Airplanes Tour '74" looking happy.
From these shots, we come to know several things. We know Russell told Rolling Stone the truth, and that they ended up running William's cover story. We know that William is enjoying family time with his mother and sister, who appear to be on much better terms than they were when they left off in 1969. We know that Stillwater rejected the big-business mentality of Dennis Hope, ditched the airplane, and went back to their "heart and soul": Doris the bus. We also know that the band is still going strong—and that Russell and Jeff haven't killed each other yet. To sum it up in musical speak, the movie certainly ends on a major note.