I took a large old drawer i had. it was about 25 x 20. painted the inside white and glued foil around the sides. had a piece of plexiglass cut to fit the top and hinged it to the top of the drawer. origianally, i put a large piece of drafting vellum on the underside of the plexiglass to diffuse the light. now i'm thinking of using either etching cream or the white stained glass paint instead of the vellum. or maybe the clearish contact paper.
i used flourescent lights from walmart. the kind you mount under cabinet. they can be linked together. then put a hole in a side for the cord to come out. i put an inline snap on switch in the cord outside to control the lights. i turned them on by the switch that is on the light itself and leave them on. then i use the inline switch to cut it off and on so i don't have to constantly open the lid. it works really well and was a total of about 15$.
i wound up making about 4 of them. one for a friend of my son and some for my nieces. i'm probably going to have to make one for my sister. it works amazingly well.