I recently had the opportunity to cook a series of yoghurt cakes. The first batch were tasty yet somewhat dense. For the second batch, I (successfully) attempted to lighten the cake by first beating the egg whites until foamy before folding in the rest of the mixture.
Both times I used fruit (raspberries) in my mixtures. For the dense batch, they 'floated' throughout the mixture. In my second, lighter batch, they all sank to the bottom.
As I found the second, lighter mixture to be better in general, is there some trick to keeping fruit from sinking like that?