If you want to see what your website looks like when someone browse using the iPad. Apple provides iPhone+iPad SDK, a tool for developer for testing application and website, but only avialable on Mac OSX.
If you don’t have the iPad or can’t find one to test it. Just check out iPad Peek, this tool let you view your website on the iPad in both vertical and verizon view. Actually, this is not the real simulator, but better have nothing.