In the early 1970s David Obst suggested to Stan Lee and Carmine Infantino that there should be a movie crossover featuring Marvel Comics' Spider-Man and DC Comics' Superman characters. However, there was already a Superman movie planned by Warner Bros. (the first Superman movie in that franchise) so instead the two companies settled for an oversize comic book entitled Superman vs. the Amazing Spider-Man: The Battle of the Century.
The comic was published in 1976 and featured the two title characters, Mary Jane Watson and Lois Lane, Jonah Jameson and Morgan Edge and the villainous Doctor Octopus and Lex Luthor. This torrent contains that book, as well as all the subsequent meetings of these two characters.
The first team-up, naturally, featured the heroes' most popular enemies, Luthor and Doc Ock. Jim Shooter clearly sought plot possibilities over Rogues Gallery prominence, and chose Dr. Doom, more typically a Fantastic Four villain, from Marvel and the Parasite, a lesser-known criminal from DC, For the second crossover.
Their third meeting was in DC vs Marvel 3-4, featuring scenes between Clark Kent and Peter Parker, as well as Ben Reilly fighting Superboy.
I also included all the appearances of Spider-boy, because hey, it's the clone of Spider-Man mixed with the clone of Superman, that's a meeting in my book. I skipped all the books that had them both on the cover, or in unrelated interior panels, and stuck with books containing interaction. Still, let me know if you see one I missed.
(It's Superman and Spider-Man, be realistic)