Spidey's best partner has always been The Human Torch. I think they have had the most team-ups out of all the super-heroes. In TASM's early days, Human Torch was appearing in almost every issue. Also a case can be made for Black Cat.
As for future team-up, I wanna see Peter team up with Agent Venom. As far as I know Pete and Flash have not teamed up since Flash bonded with the symbiote.