Dashboard for the iPad was rejected by Apple, but was made open source. This means if you have a developer account you can load it up on your iPad to play with! You can download the source code here and start playing with it. It seems a little slow but works amazing well. You can even download new widgets right in the app. I am sure Apple did not approve this because they want to steal the idea and bring it into an update later down the road. If you would like to test this out along with the iPhone OS 4.0, LEI Mobile is offering spots on their dev team for a small donation! Check it out here.
in simulator this works fairly good, its missing the whole popover the destkop but you kno its a pretty good concept