user7186: Is it possible to connect 6 dc motors and 2 dc servo motors to an Arduino Uno? I intend to control the Uno with a Raspberry pi connected through USB.
Assuming every motor to be bidirectional, how many L293 or L298 motor driver boards do I need? Is there any other better option than using multiple driver boards?

user6854: TI is only one of the many manufacturers who make some really nice motor control chips.  The  DRV8835 is one such device: it will drive two motors at voltages up to 11 Vdc at currents up to 1.2 Amps each.  Each channel requires two control lines: enable and direction.
Pololu sells this chip already mounted to a carrier board for a rational price.
You will need a total of (6 motors * 2 lines per motor) = 12 i/o lines PLUS two more lines to control your servos for a total of 14 i/o lines from your controller.

7186: <p>Is it possible to connect 6 dc motors and 2 dc servo motors to an Arduino Uno? I intend to control the Uno with a Raspberry pi connected through USB.</p>

<p>Assuming every motor to be bidirectional, how many L293 or L298 motor driver boards do I need? Is there any other better option than using multiple driver boards?</p>
 6854: <p>TI is only one of the many manufacturers who make some really nice motor control chips.  The  DRV8835 is one such device: it will drive two motors at voltages up to 11 Vdc at currents up to 1.2 Amps each.  Each channel requires two control lines: enable and direction.</p>

<p><a href="https://www.pololu.com/product/2135" rel="nofollow">Pololu</a> sells this chip already mounted to a carrier board for a rational price.</p>

<p>You will need a total of (6 motors * 2 lines per motor) = 12 i/o lines PLUS two more lines to control your servos for a total of 14 i/o lines from your controller.</p>
