If you want to make a box of lasers, first you'll need a box or treasure chest. This one was made from reclaimed wood by my talented carpenter friend Hudson. Line the box with some red velvet for bonus pizzazz.
Step 1: Mount lasers on a tripod
You'll need four Class IIIa (5 mW) laser pointers, any combination of blue, green, and red. Blue and green appear brighter than red at the same power output because the eye is more sensitive in the blue-green wavelength region, so I use all blue and green. For eye safety reasons, I don't recommend using higher powered lasers. The beam will generally be split into lots of smaller beams and therefore won't hurt anyone who accidentally looks into the light, but there's no safety mechanism in place to prevent someone from taking an eyeful of un-split laser beam (which could fry an eyeball before the blink reflex kicked in if you used a higher-powered beam).
Remove the back ends from the lasers. For each laser, use one red and one black alligator clip. The black one should be clipped to the center coil and red one should be clipped onto the outer cylinder as electrical contacts. It helps to use two different colors because the laser pointers have polarity and won't work if they're attached backwards.
Put rubber bands around the laser pointers to keep their push-buttons pushed in. Rubber band the whole mess together on a mini-tripod (I'm using a Joby Gorillapod.)
Step 2: A place to put the batteries
The circuit is dead simple: run wires from the laser to a switch, to a 2xD battery pack, back to the laser. If it's wired so that the laser works with the black alligator clip clipped to the center coil in the laser, you can use the mnemonic "red to edge" when attaching the alligator clips to remember which way they go.
The battery box is a Fraggle Rock lunchbox (recommended), but any lunchbox will suffice. Also makes a great place to keep spare batteries, rubber bands, lasers, and maybe some lunch. Because the box is metal, it's super important to make sure there are no exposed wires that could short out, so use lots of heat shrink tubing as necessary.
Two D batteries are sufficient to power a 5 mW laser for a LONG time, like probably several days straight. If it's worth doing, it's worth overdoing.
Step 3: Attach rotating stand
The rotating stand needs to support at least 2 pounds and rotate slowly for many hours. Rotating display stands work great for the purpose.
Drill 2 holes opposite each other on the sides of the stand near the bottom, and use those holes to ziptie the stand onto the surface below it (i.e. a piece of plywood, or in this case a vintage metal sign advertising Bovril). Attach strips of velcro to the top of the rotating stand -- we don't want anything to fall off the stand and break.
Step 4: Add cut glass treasures
In the drawer, we have some interesting chalices, candy bowls, glasses, etc, with interesting cut glass patterns to diffract the light. It's hard to predict what kind of glassware will produce nice patterns, so it helps to bring a laser pointer to the thrift store to try shining it through different objects.
People may look at you like you're a lunatic when you shine a laser pointer around the kitchenware section of Goodwill, but they don't actually throw you out of the store.
Make sure to superglue a strip of velcro onto the bottom of each one so they stay on the rotating stand.
Step 5: Rotomatic party in a box goes everywhere!
Smaller than a carry-on bag, sturdy, quiet, the Rotomatic is the perfect traveling companion. Also makes a great end table. Check it out projecting onto a ~20'x40' white wall: