There are optical-domain attacks for CRT monitors (including diffuse reflections off walls from the "blue glow"), likely similar for LCDs. And there are Van Eck attacks on CRTs and LCDs. Cables don't usually leak by definition of twisted pair and coaxial being solenoids (the ideal model of solenoids emanate zero net EM flux at distance and immune to external EM fields), but connectors, unshielded traces, straight wires, untwisted ends of twisted pair and component joints tend to be the usual suspects.
http://www.cl.cam.ac.uk/~mgk25/ieee02-optical.pdf
http://www.cl.cam.ac.uk/~mgk25/pet2004-fpd.pdf
http://www.hack247.co.uk/blogpost/van-eck-phreaking/ (unscientific/not peer-reviewed)