Can i control more then 2 dc motors (3) using

using motor control shield?

Please help me figure a way to control a third motor, I only need to control the polarity (direction) of it (not it speed).

Can I connect one wire of the motor to GND and the other to Digial output?

for a reverse direction I can also connect the same wire that is connected to GND to digital 2 and the wire that is connected to digital 1 to GND...

Thanks!

I only need to control the polarity (direction)

It is the direction control that takes up the resource on a motor shield. Given one H bridge you can control either one motor in a bi directional manor or two motors in a unidirectional manor.
Any more that this and you need another control circuit.

Can I connect one wire of the motor to GND and the other to Digial output?

No you can't connect a motor directly to an arduino, it needs to go through a bridge.:-
http://www.thebox.myzen.co.uk/Workshop/Motors_1.html
and
http://www.thebox.myzen.co.uk/Workshop/Motors_2.html

Thank you for your answer.
Can I connect servo to the motor control shield (and still use the 2 dc motors)?

Servos don't need a large current to control them just a logic signal, so there is no need to connect a servo to a motor shield at all. Just connect it to a normal output pin.
It will however probably need an independent supply (with common ground)

If you are using the ladyada motor shield then you can connect up to 4 DC motors. Most motor shields will let you use more than 2 motors.

Mowcius