In graduate school I used liquid nitrogen to freeze a solvated reagent used in a highly exothermic reaction. That allowed me to make large amounts of product without a volcanic eruption from the reaction flask.
I have given various demonstrations of the properties of liquid nitrogen including ice cream making, balloon shrinking, lead ringing, super conductivity, etc.
For some time I had liquid nitrogen delivered to my home by a cattle breeding service. The main customers of the service were for the semen tanks at dairies or other breeding operations. Unfortunately, the service only delivered every other month. That is frequent enough to keep semen frozen, but not often enough if you want to play with liquid nitrogen. Now, I could go to a welding shop to pick it up if I needed it, but that would mean that I would actually have to plan ahead.
A few years back I located a company that sold LN2 generators for about $20,000. Definitely out of my league at the time. Last summer I found a company on the web that puts out an Elan 2 liquid nitrogen generator with a 20 liter or so dewar. They have a similar version with a 1 liter dewar for doctor's offices. (Used for wart freezing, I presume.) I sent an email off for a quote on the price and never heard back.
Now, Halloween is a busy day for me. I live in the classic suburban area where every kid for a thousand miles around descends like a locust. I was so busy handing out candy that I never had time to read my email last Halloween. Then I few days ago, I was checking old emails for some reason and found a reply from the company. The price is $13,500. Ridiculous! I can't afford that! Except I can. I have the money in the bank. That money is for a new car. My current car is 11 years old. My mortgage is paid for. I am saving that much a year. If my car can hold together for just one more year...
I mean, liquid nitrogen on tap!
Somebody stop me!!! Aaaaeeee!