I will answer part of this. NNN mobi and mixed letter/number (which are called three character) .Net and .Org have little value, you might get $25 with luck, maybe.
Last I looked three character .coms were low three figures.
Look here for info on all 3 character domains: http://3character.com/priceguide.html (not mine) -- Still a great site although it is 6 months out of date.