With the advent of the iPad, aPad, and other touch-sensitive tablets, my bet for money-making investment right now is companies who produce microfiber cleaning cloths!  It doesn't take long for the screens of these things to get quite grungy and this seems to be the best thing to clean them.  I have been fiddling with an iPad for about a week now, and I just used my cleaning cloth from my eyeglasses.  It did a great job, but since it's not large, it was a bit fiddly.  So take my advice, and invest in one of these companies.  Oh, yea, and when you are rich, send me a buck or two, okay?