Are there other characters with combined techniques in Dragon Ball other than Gohan and Piccolo's Demon Flash of Death? Spoilers from manga 56


   For trying to defeat 73, Gohan and Piccolo use a combined technique called Demon's Flash of Death, (Masenkōkōsappō) a combination of Demon's Flash of Light (Masenko) and Special Beam Cannon ("Demon's Penetrating, Killing Light Gun", Makankōsappō)


Are there other characters with combined techniques like them in the series?
You can find some on the wiki under Team Attacks or Combined Techniques.
As an example the Final Kamehameha of Goku and Vegeta:


  Final Kamehameha (ファイナルかめはめ波 Fainaru Kamehameha, lit. "Final Kamehame Wave") is a combination of Goku's Kamehameha and Vegeta's Final Flash used by Vegito. The move can also be created when Goku and Vegeta combine the Super Kamehameha and the Final Flash simultaneously.