You can get little bottles of isopropyl alcohol from record stores like HMV. A few drops round the disc, wiped off with a lint-free cloth from the inside to the outside works great.
Not sure whether it's really any better than soapy water though.
Firstly, you should never need to clean DVDs & CDs; If you always hold them by their edges and keep them in their cases, when not in use, they shouldn't need cleaning.
However, nobody's perfect! I've sometimes cleaned CDs and DVDs. As suggested, warm soapy water is fine. (At least, I've never had any problems!). Dry them gently with kitchen towel.
I've found with CDs that don't play properly any white spirit (NOT WHITE SPIRIT) eg Vodka/Gin/Tequila works really well.
My mate who was a DJ reckoned flicking cigarette ash on them helped, but I can't see why