Is your Dashboard cluttered with tons of widgets that you don't want to see any longer? You can easily hide widgets from your Dashboard by holding down the option key while mousing over top of your widget and clicking the "x" button that shows up.
Clicking the "x" button does not, however, delete the widget -- it will only hide it. To delete a widget, click the "+" button in the bottom left corner (or hit the command and + key combo) then select the "Manage Widgets..." button. From this widget manager, you will be able to click the red minus button beside the widget to completely remove it from your Mac. The deleted widget will show up in the OS X trash can.