So many situations and so many different songs. I seldom listen to music when I ride, but I do play it in my head or sing out loud. For me they tend to be situational. "30,000 pounds of bananas" is likely to be in my head on any steep multi mile mountain descent. I couldn't resist singing "I fought the law and the law won" when passing a chain gang soing road work. My female companions probably hated my rendition of "fat bottom girls".
Oh and "bicycle race" by Queen pops into my head sometimes. Otherwise stuff like " the wind cries Mary" or Ben Sollee's "sweet Marie".