Here is a second instructable for a lamp made out of an empty plastic wash-liquid bottle.
More ideas like this are featured in a free downloadeble ebook on my website www.ruudvankoningsbrugge.nl/flessenboek
sorry this is in dutch, but the google translator works wonders. Eehhh, yeah, wondrous wonders most of the time. The pictures and drawings are no problem for anyone.

Step 1: All Parts

You will need:
an emty detergent bottle
a simple lampstand ( i bought one cheap in a house deco shop)
a bottlecap of a other bottle ( The top should fit snug inside the rim of the bottle)
small ring of bicycle innertube
A sharp knife
small hacksaw
scissors

Step 2: The Connection Bit

Cut of the top of the bottlecap with a hacksaw. Make a hole the same size as the lamp socket. I used a sharp knife.

Step 3: The Fitting

screw the bottle-cap ring on the socket.

Step 4: Reshape the Bottle

Cut off the bottom of the bottle. Design an interesting shape witch fits the handle of the bottle and cut out.
Place the bottle over the rim on the socket. I had the luck it fitted perfect but you could use some ( doublesided) tape to make it fit.
I covered the screw-thread of the bottle with an elastic band cut from a bicycle tyre.