I really like The Weather Network. They just recently updated the app and made some really nice improvements. The widget is great as it is only 2x1 and displays the current conditions. You can choose different cities for the widget or your can choose to use the location services, so if you move to a different city, it will automatically give you the current conditions for that city. The only down side is that there is not tablet version yet.
For my tablet, I use The Weather Channel app instead.