Just off the top of my head:
Green Arrow and Speedy (DC Comics)
Captain America and Bucky (Captain America Comics/All-Select/USA Comics/Timely)
Sandman and Sandy (Adventure Comics/DC)
Human Torch and Toro (Timely Comics)
Captain Wonder and Tim (Kid Komics-Timely)
The Defender and Rusty (USA Comics-Timely)
Shield and Dusty, the Boy Detective (MLJ)
Black Terror and Tim (Better/Nedor)
American Eagle and Eaglet (Better/Nedor)
The Wizard and Roy (MLJ)
The Flagman and Rusty (Holyoke)
The Catman and Kitten (Holyoke)
Blue Beetle and Sparky (Holyoke)
Lone Warrior and Dicky (Banner Comics and Captain Courageous Comics from Ace Comics)
The Eagle and Buddy (Fox Publications)
Green Mask and Domino (Fox Publications)
The Dart and Ace (Fox Publications)
Samson and David (Fox Publications)
The Lynx and Blackie the Mystery Boy (Mystery Men Comics-Fox Publications)
Black Lion and the Cub (Wonderworld Comics)
Nightmare and Sleepy (Clue Comics)
Black Cobra and Cobra Kid (Ajax Farrell)
Fighting American and Speedboy (1950's)
And those are just the teen sidekicks. For instance, the Star Spangled Kid was a teen superhero who had a sidekick, Stripesy, who was also his alter-ego's adult chauffeur. Then there were the numerous "comic" sidekicks like Doiby Dickles and Green Lantern.
Anyway, that's the tip of the iceberg.