A few compatible Dashboard widgets (BART, Tile Game, Super Brain, and Whoopee) are setup by default apps in PointAtMe to demonstrate that Dashboard widgets can be run without any modification on the iPhone.. Expect more Dashboard apps to become iPhone friendly as developers get hold of iPhones.
In my search for Dashboard widgets to include, there were many that could probably work, but need to be hosted on the widget developer's website. Examples would include AppleDailySpecial, DailyTao, ESPN, Nature Science, and Package Tracker.
And, there are some widgets that will simple never work on the iPhone until Apple allows native support for them because they use plugins that aren't support on the phone.