I saw that someone had posted a link to my liquid nitrogen page. I've written a very complete tutorial on how one can generate liquid nitrogen at about 350 cc/hr using readily available supplies. I will answer any questions.
The tutorial is here.
I readers would like, I can add another tutorial on the pressure swing adsorber that I made to generate 98.5% nitrogen gas from air. This is also useful if one wants pure nitrogen to fill tires.