Connect XBee to Arduino without shield
Yes, all you need to do is logic level conversion. 

Adafruit does that by using 74HC125 buffer: 



You can set up the same schematics on your breadboard or use it in your custom design. If you have Arduino Uno rev3, you can skip +3.3V regulator as Arduino provides a capable +3.3V regulator on board.

The schematics picure is from Adafruit page.