1.Lightscribe is a technology used in some optical disc drives in which the drives laser can be used to burn text and graphics onto the surface of a special LightScribe disc.
2.I don't think there are any external LightScribe drives available right now. But if they are, i think they can be connected to a laptop.
3.UMD (Universal Media Disc) used in Sony's PSP (not PlayStation 2) is a proprietary format developed by Sony only for the PSP. Hence naturally it can only be played on a PSP. Also it is too small to fit in any PC's disc drive.