expected unqualified-id before 'if'

/*
  # Auto waterer
  # Editor     : Mike
  # Date       : 1/25.2013
  # Version    : 1.0
  # Connect the sensor analog out to the A0(Analog 0) pin on the Arduino board
  # Connect the sensor VCC pin to 5v pin on Arduino the board
  # Connect the sensor GND pin to GND pin on the Arduino board.
  # the sensor value description
  # 0  ~300     dry soil
  # 300~700     humid soil
  # 700~950     in water
*/
#include <Servo.h>
Servo myservo;           // create servo object to control a servo
int moisturesensor = 0;  // analog pin used to connect the moisture sensor
int val;                 // variable to read the value from the analog pin

void setup()
{
  Serial.begin(57600);
  myservo.attach(1);       // attaches the servo on pin 1 to the servo object
  pinMode(moisturesensor, INPUT); // Assigns sensor to pin 0
}

void loop()
{

  moisturesensor = analogRead(0);   // reads the value of the sensor (value between 0 and 950)
}

if (moisturesensor < 300)          // if soil is dry
{                                   // open water
  myservo.write(90);      // sets the servo position according to the sensor value.
  delay(15);             // waits for the servo to get there
}

else
{
  myservo.write(0);      // turns the water off
  delay(15);             // waits for the servo to get there
}

void loop()
{

moisturesensor = analogRead(0); // reads the value of the sensor (value between 0 and 950)
} <<< what does this do?

This is your entire loop now:

void loop()
{

  moisturesensor = analogRead(0);   // reads the value of the sensor (value between 0 and 950)
}

The stuff that follows is not part of loop.
You probably want to delete the } and put it at the end of the code.

Is 15mS enough time for the servo to move? Seems pretty quick.