The U.K.'s Now series features timely selections of pop hits and provides a convenient way for casual pop fans to stay on top of the most popular singles. The sets are almost always naturally well-rounded, encompassing dance music, R&B, hip-hop, teen pop, and rock. And though they might expire, in a sense, since they're based on trends in pop music, they work as more than adequate snapshots of specific points in time. Now 55, released in 2003, includes R. Kelly's "Ignition," t.A.T.u.'s "Not Gonna Get Us," Jay-Z's "Excuse Me Miss," 50 Cent's "In da Club," Wayne Wonder's "No Letting Go," and Girls Aloud's "No Good Advice."