If you're new to Arduino, you might not realize just how badly delays can impact performance. When (not if) you run into problems associated with delay - the Googles might have you believe that a library is the answer to your problems. It can help... but may not be necessary. Consider the following approach as an alternative.

Millis_Slice.ino

byte LED = 13;           // debug LED on the Arduino
byte blnk = 0;           // variable used to track LED flip-flop

unsigned long tme = 0;   // the last time we processed doBlink()
unsigned long slc = 500; // milliseconds between doBlink() calls
unsigned long ms = 0;    // a millis() time-slice

void setup() {
  pinMode( LED, OUTPUT );// set Arduino LED as output - for to blink
}

void loop() {
  ms = millis();

  // are we ready to call doBlink()?
  if ( tme + slc < ms ) {
    tme = ms;
    doBlink();
  }  
}

void doBlink() {
  if ( blnk == 0 ) {
    digitalWrite( LED, HIGH );
    blnk = 1;
  }
  else {
    digitalWrite( LED, LOW );
    blnk = 0;  
  }
}