How can I unlock and configure my Nexus One without a SIM card? I have a Nexus One which I want to send to my mother.  Where do I go to have it unlocked?

Does it run the latest version of Android and can I install apps without a SIM card?
If you mean unlocked so any SIM can be used, the device comes from Google SIM Unlocked. 

From Wikipedia Article:


  The device is sold SIM unlocked (not restricted to use on a single network provider). Google offered T-Mobile USA and AT&amp;T versions of the phone online in the United States before closing the online store in July 2010. 


The difference between the AT&amp;T and T-Mobile version is the bands that the phone uses for its network. If you don't have the right bands, the network will fall back to the common network, which is EDGE. For example, if you have a T-Mobile version, and you mother has AT&amp;T, then when she is browsing the internet she will only get EDGE(2G) speeds. Voice there really is not noticeable difference.

So to answer your question, you don't have to take it anywhere, and it costs nothing extra. You paid for it to be unlocked when you bought it. 

You should be able to install applications without having a SIM card. At the very least, you will need to have wifi available so you can download the applications. I would suggest a factory reset, then start the device and configure it how you want for your mother, with apps, and email setup, etc.