I searched for lava lamps i only found lamps which was necessary put alka-seltzer to work, what i consider a fake lava lamp.
Me and my colleague have decided do the same project and make an instructable, he posted the project 1st and he got all the profit xD.
What you need is:
an aluminum can
a colorless glass bottle
2 BOTTLES OF ALCOHOL
Step 1: Preparing the Bottle
Put a few drops of colorant in the alcohol and shake (I used red)
Put the oil in the bottle (isn't necessary paint it)
fill the bottle with the already painted alcohol and go adding water when the oil rise, stop there.
close the bottle (I noticed when the lamp warms a lot content in the bottle tends to rise out of the bottle, so i recommend don't fill up at max)
Step 2: Doing the Electrics
Glue the lamp socket in the can lid, you also can use wood or any metal to support the lamp.
Step 3: Preparing the Can
Cut a net disk to put over the hole made before
Drill a hole in the can to pass the wire
Put the cap on the bottom of the can
opcional- wrap the can with aluminum foil (to look better).
Step 4: Done
if the oil dont don't rise add water or if the oil is always on top add alcohol.
Sorry for my bad english. :)