Need to control rc model relays (that operartes high-voltage motors). Is it possible to make with RPi without additional hardware? Any links to the solution?
Not a conventional relay, you'd have to use a very small relay (if you can find one with a 3.3V@16mA or less coil) to switch a larger one and then be careful that the back EMF didn't damage the GPIO pin.
Much better idea to just use a transistor if it's just a single relay
However it may be possible to find a solid state relay that's suitable. Although they tend to be more expensive than a transistor+conventional relay.
not without additional hardware. I would take look at those arduino motor shields... they are capable of controlling several motors.
If you want to control a servo instead of controlling a motor directly, thw pwm output of the raspberry will help you - and no additonal hardware is needed because the servo already contains it. But afaik, the raspberry only has one pwm output - so you will only be able to control one servo easily. If you need to control several servos, a servo controller like this one will be helpful: http://seetron.com/sscasd2.html