If you are willing to add a liqueur, substitute a raspberry flavored liqueur for part of the liquid - 1/4 or 1/3 cup should be enough. It makes a huge taste difference. If you also add raspberries, it makes a nice sweet/tart combo. If I can't find fresh raspberries I use fresh frozen, don't thaw. After your batter is in the pan, sprinkle a few berries over the top and lightly press in.
Icing fruits are the bomb!
That's for sure. I had locked into a clearance of $1 a jar, a couple of years ago. I wish I would have bought it by the case, but I didn't have the cash at the time.
Theresa 
What about adding fresh raspberries and some raspberry extract to a white cake batter?
you can add raspberry icing fruit to your white cake recipe. Icing fruits are the bomb!
countrykitchensweetart.com
How long are they good for once you open them? Can you freeze it?
I use raspberry flavored coffee syrup by Torani along with a tsp or two of extract when I make my raspberry lemonade cake. It works well, and makes a nice pink colored cake.
I don't make cakes with the fruit cooked inside. So this is an option. Make your regular white or yellow cake. I brush the tops with liqueur, in this case Chambord. Jam, fruit, or a combination, along with extract can be added to the buttercream for two layers. On the middle layer, I add a layer of jam, thinly spread. The frosting can be the same as the filling or just have the jam in it, leaving the fruit for the filling. I top the cake with the fruit or the fruit that has been half dipped in chocolate.
try this delicious buttermilk cake by Smitten Kitchen, http://smittenkitchen.com/2009/05/raspberry-buttermilk-cake/ - so moist and yummy, it uses raspberries baked in.
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