Google Nexus One Unlocked
The Google Nexus One unlocked works with most SIM cards and therefore doesn’t require further unlocking using an unlock code or advanced unlocking software. If you decide to purchase the non unlocked Google Nexus One it is currently only available with T-Mobile for $179.99. This is much cheaper then the unlocked Google Nexus One which will run you about $529.00. There is a significant price difference between the two types of phones, and many people have already been able to unlock and root their Google Nexus One. Doing this could be cheaper in the long run for you, if you do not wish to have service with T-Mobile. If you want to learn more about wheather your SIM card will work in an unlocked Google Nexus One, you can check out this page.
Otherwise, you can watch this video I found on YouTube recently that demonstrates the free unlocking and rooting of a new Google Nexus One. Enjoy! 
Getting An Unlock Code
If you are unable to get a free unlock code from your phone carrier, then check out this website that offers unlock codes for many different phone models at a low price.
