I used to use a bendy desk lamp to light up the print bed but it didn't work too well so I bought a bunch of cheap USB LED strips from Amazon (http://www.amazon.com/gp/product/B00198L9RA/ref=oh_details_o02_s00_i00) and then designed this mount to attach to the Y rods on my Prusa. It lights up the bed pretty well with nice clean light.

1) Buy some of these: http://www.amazon.com/gp/product/B00198L9RA/ref=oh_details_o02_s00_i00
2) Print one mount and two clips for each LED strip you want to install.
3) Slide the clips onto the LED strip.
4) Insert the clips into the mount.
5) Snap the mount onto your Y rods using a twisting action.