i call it a bubble lamp and not a lava lamp because in its off state the "lava" sits at the top of the bottle, but as it is turned on and heated the wax sinks according to the room temperature and remains a static bubble.
you will need:
+ power plug
+ glass bottle
+ metallic bottle holder (angle iron)
+ rubbing alcohol
+ paraffin wax
+ 30 watt globe
Step 1: Base & switch
you could go with the easier option of using a cable mounted switch. but i enjoy making mechanisms and creating more work for myself. so i went for creating a rotary switch using a brass knob from a drawer. i threaded a bolt into it and welded a washer off center to touch the switch, the video should explain.
invalid movie: http://www.vimeo.com/5487773
the base can be made out of whatever you want i used wood because it has a nice finish and made it much easier for me to router the shapes to create my switch.