This is something that Flex excels at. Perhaps the only thing that I really miss.

For instance, in flex, to do a 3 column layout, I could do something like:

  <HBox>
     <VBox width="33%">
       [Content]
     </VBox>
     <VBox width="33%">
       [Content]
     </VBox>
     <VBox width="33%">
       [Content]
     </VBox>
  </HBox>