I have heard alot that pineapple wine needs a very long time to age correctly. It may be the same with raspberries, seeing that they are both possibly tart fruits. you are probably best off if you just let them age for a good long time. sweetening is another option as stated above. someone more knowledgeable about wine may have some tips on this also.
Primary: blueberry apple cider
Secondary: panty dropper cranberry apple cider
bottled: I should probably get some of those...
on deck: future brews suspended for the moment :(...