I was trying to use my Arduino Uno as a USB to Serial TTL explorer rather than buying an FTDI FT232R type board. I read where this could be accomplished by removing the Atmega328P microcontroller and just letting the Atmega8U2 handle the job. I read several places that all I had to do was remove the 328P and use pins 0 and 1 for TX and RX. Well, that didnt work, I couldnt communicate with my XBee's. So I was able to find a reference schematic for the entire Arduino Uno. Turns out the RX wire on the 8U2 is connected to the TX pin on the 328P and to digital pin 1 (labeled TX); also, the TX wire on the 8U2 is connected to the RX pin on the 328P and digital pin 0 (labeled RX). So I had to connect the Arduino RX digital pin 0 to the RX pin on the XBee and the Arduino TX digital pin 1 to the TX pin on the XBee and it worked fine. I just wanted to post this for anybody else trying to accomplish what I was trying to. I read no where that you had to reverse the pins 0 and 1. In hindsight it makes perfect sense, though. The 8U2 transmits out and the 328P must receive it, and vice versa.
After I reversed the TX and RX wires on my breadboard I was able to open a serial terminal window and communicate directly to my XBee as intended.