I went to this lecture at Cal Tech back during my own AP chem class, anyway one of the speakers did the hand thing and it worked perfectly, well acctually the assistant did it. No freezer burns or anything, just make sure you pour and not dip
Have Fun
We used The stuff to freeze seal pipes.Great fun to dip a racquet ball in it,bounce it and watch it shatter like a lightbulb.
You don’t really want to know about some of the things I’ve
done with LN2. Well, maybe you do but I would be guilty of
corrupting the Teeming Millions if I told you.
About the most fun and unexpected “trick” was similar to
many of the suggestions here about letting it spread on
the floor and dance around. In the case I have in mind,
“dance” was more literal.
One day when we were playing with some Tygon and LN2,
the lunchroom got invaded by ants. We noticed when we
spilled some nitrogen on the concrete floor and the
skittering droplets intersected the trail of insects.
You would think that the little critters might get frozen
and die and you’d be right, but we didn’t expect them to
absorb the stuff and start popping and spinning wildly
like a troupe of little break-dancers!
Much better than bug spray: instant results and no messy
residue. Subsequent applications of our new exterminator
technology were of course accompanied by appropriate music.
I read an account once (I’m pretty sure it was on the Web) of a graduate student who drank a mouthful of liquid nitrogen, believing it to be harmless.
It put him in a coma for days, and he suffered severe trauma to his esophagus, trachea, sinus cavity and lungs.
(This is all as I remember it; I just did a quick Web search and was unable to find the story again.)
Apparently, while it’s safe to hold as much as a mouthful of liquid N[sub]2[/sub] in, well, your mouth, you do NOT want to swallow.
Do your required experiments include working with magnets or electricity? Some (all?) metals become superconductors when
superchilled. Similarly, magnets become superstrong when immersed in liquified gases. I think nitrogen would be cold enough. I think you could put some liquid N into a beaker on the lab table, and drop a small ordinary magnet into said beaker. I think a refrigerator magnet would do. Then, try sticking heavy metal objects to the underside of the table. You could try a heavy wrench, for example. Tie a string to the wrench and tie the other end to a leg of the table, and see if the magnet can hold the magnet up in mid-air. Or get some iron filings and see how much better the patterns of force can be seen around the magnet.
We messed with LN2 in a college thermodynamics class. The only thing I can think of that hasn’t been suggested is paramagnetism. This memory was of course inspired by javaman.
While liquid nitrogen is not cold enough to cause superconductivity (except in those cool high-temp ceramics), it is cold enough to convert certain non-magnetic metals into magnetic ones. I can’t recall which ones they are (boron? beryllium?), but you should be able to look up paramagnetism for the proper info.
These metals won’t stick to a magnet at room temp, but will when chilled by the nitrogen. Hang a magnet by a string and dangle it near the chilled metal. Get it only close enough to make the string hang at an angle. Leave it there for a minute or so, and watch how the magnet slowly moves away from the metal as it warms up.
Well, it ain’t explosive, but it’s interesting. Educational, even.
The Leidenfrost effect is real SouprChckn. I can’t take legal responsibility of course, but I’ve tried it with nothing bad happening. I once had a corn removed from my finger with LN2. The doctor dipped a Q-tip into LN2 and had to press down real hard to make it work. It took several applications of that before the top layer of my skin died, and even then it didn’t hurt much (about as much as pulling of a bandaid with your body hair). Like I said, start with a small drop if you’re afraid. Do it in the back of the classroom so you can avoid the embarrassment 
Well I was ready to try and test the Leidenfrost effect for myself but my teacher wouldn’t give it to me once she realized that I was going to possibly inflict bodily harm to myself. I guess I’ll have to try it out on my own time but I managed to try a few other things. Freaking people out with my nitrogen breath. Putting stuff in the LN2 and smashing it. At one point, she was filling up our container w/ more LN2 and the cup got so cold it busted open at the bottom and started spilling everywhere. There wasn’t enough to cause a disaster but it sure was cool to see it boil before it hit the ground.