I made it possible to run the DrawBot by feeding it an array. Haven't tested since I don't have servos.

raster's drawbot

/*
 * Drawbot.pde
 */

#include <Servo.h> 

Servo leftServo;
Servo rightServo;

int servoPinL = 9;
int servoPinR = 10;
int a, i;

int servo_delay = 15; // 15 millisecond servo_delay between servo steps.
int servo_speed = 180; // Actually the angle the servo should go to, but we're using continuous
int length = 8; // How long the instructions array is + 1 for null char. Needs to be updated when instructions array changes.

// Instructions: r = right, l = left, f = forward, b = backwards.
char instructions[] = "rrllfbfb";


void setup() {
  leftServo.attach(servoPinL);
  rightServo.attach(servoPinR);
}

void loop() {
  for (i = 0; i < length; i += 1) {
    switch(instructions[i]) {
      case 'r':
        right();
        break;
      case 'l':
        left();
        break;
      case 'b':
        back();
        break;
      default:
      case 'f':
        forward();
        break;
    }
    delay(servo_delay); 
  }
}

void right() {
  for(a = 0; a < servo_speed; a += 1) {
    leftServo.write(-a);
    rightServo.write(a);
    delay(servo_delay);
  }
  leftServo.write(0);
  rightServo.write(0);
  delay(servo_delay);

}

void left() {
  for(a = 0; a < servo_speed; a++) {
    leftServo.write(a);
    rightServo.write(-a);
    delay(servo_delay);
  }
  leftServo.write(0);
  rightServo.write(0);
  delay(servo_delay);
}

void forward() {
  for(a = 0; a < servo_speed; a++) {
    leftServo.write(a);
    rightServo.write(a);
    delay(servo_delay);
  }
  leftServo.write(0);
  rightServo.write(0);
  delay(servo_delay);
}

void back() {
  for(a = 0; a < servo_speed; a++) {
    leftServo.write(-a);
    rightServo.write(-a);
    delay(servo_delay);
  }
  leftServo.write(0);
  rightServo.write(0);
  delay(servo_delay);
}