If you tell me the area code and prefix I can confirm it’s a cellular number and the city it’s associated with (please don’t include the last four). I use my DeLorme Street Atlas program for this.
You could look in the reverse directory at http://www.anywho.com if it’s not a cellular number. I did hear something months ago that cellular numbers were eventually going to be listed like land based numbers, but I haven’t seen it yet.
You can go to http://telcodata.us to find out who a number is assigned to, at least the area code + prefix.
However, remember that with number portability, the number you’re looking for may have been ported to another carrier, and as such, you’ll only know who the original assignment was.