The Ext GWT 3 grid doesn't have any particular UiBinder-related features, so you can include it in your UiBinder template like any other widget.
Notably, because Grid needs constructor arguments, you will need to construct the Grid in code. Take a look at http://code.google.com/webtoolkit/do...Using_a_widget. If you want the grid to be constructed when your UiBinder is constructed (that is, you're not reusing an older grid instance), you will probably want to write a UiFactory method. Follow the examples in that link; instead of creating a new CricketScores, you'll be creating a Grid.