Download the code on from my Google Drive. The RF24 and RF24Audio folders are libraries and need to be placed in the Arduino's library folder per these instructions. The walkie_talkie_basic file is the code that you will open up in the Arduino's IDE.
Microphone circuit for person to speak into. Transistor amplifies the sound wave from the electret microphone and outputs the data to the Arduino's analog in 0.
Simple button circuit for "talking" while the person on the other end is listening.
I used the long range nRF24L01 modules, but the short range ones will work as well. Also attached is the pinout for the nRF24L01 courtesy of the guys and gals over at ArduinoInfo.Info.