You can rotate the iPad with a click on the border.
This is an iPad demo site. You can simply enter any website here and you will see a demo of how it would look like on an iPad. Remember that Flash works here, but it wont work on the iPad. There are other minor differences, but you get the idea.
You can preload a page or set portrait mode by passing using URL parameters, like this: http://ipaddemo.net/?url=google.com&portrait
A great tool made by stick84. Thanks man! You can also get the code here.