This may be a lame question but, Speed controllers on big RC cars can they be controlled from Arduino? If yes, do they have a standart? do I control them using PWM values? What should i look for if I am going to buy one?
They should be controlled by pwm, in particular the same pwm that is used for servos. Typically built in pwm units are not accurate enough, instead interrupt driven timer routines are usually the way to go. Should be lots of info on the web for arduino and servos.