After Apple released their iPad, many other vendors prepared to release their own product that soon will be a rival to Apple's iPad. Google for example, is preparing to release their own product, which is rumored to be GPad and it's running Google Chrome OS. The video is already posted on Youtube by Glen Murphy, one of Google's Chrome OS designers.
Here's the preview of the gPad (prototype)
Another contender comes from WePad, designed by a German company. It's really designed to be an iPad killer, since it has 11.6-inch screen, definitely bigger than iPad's 9.7-inc, powered by an Intel chip and relies on a Linux software basis which is compatible with Google's Android and all Flash applications, something that Apple doesn't have (especially Flash, in which their battle is going hot and hotter howadays).
It's also said that WePad users are not required to install specific application to put their files on the WePad, unlike Apple with iTunes. Since it's Linux-based, it should be compatible with all operating systems available. This is surely strike Apple since Apple is well known of their iTunes as a gateway to their products.