Raspberry jam is usually good for filling a cake. Just mix with a little buttercream. Also Wilton has a recipe for a raspberry filling here http://www.wilton.com/recipes/recipesandprojects/cake_filling/raspberryfilling.cfm
Hopefully this is what you are looking for.
I haven't used raspberries, but I've made a strawberry filling by mixing softened cream cheese with strawberry jam. I would imagine that softnened cream cheese with raspberry jam would taste great, too.
Just raspberry jam alone won't give you a fresh raspberry taste. If you want a filling that has a custard-y pastry cream consistency that will stand up to stacking, make a french buttercream ( I use the Neo-classic buttercream recipe from the Cake Bible). In lieu of the 1 c. liqueur, and 1/4 c. seedless raspberry jam ( the English brand Dickenson is the best I've ever had) , 1/4 c. raspberry puree, and 1/4 c. Chambord.
It'll blow your mind how good it is.
Txkat - that sounds really good! I've never made a french buttercream - can you add puree & liqueur to an italian meringue bc? And did i read that right - if you use the Cake Bible recipe, reduce the liqueur to 1/4 c when using pureed raspberries? Sounds delish! Back to the library to take out the Cake Bible!
The french buttercream recipe in the cake Bible is called Neo-classic buttercream, and I mentioned it specifically because she mentioned pastry cream. Neoclassic buttercream is egg yolk based, as is pastry cream, thus giving you a similar taste and texture. I imagine it would work with an italian or swiss merigue buttercream as well, but the texture on those icings is different.
When I add them to the icing I warm the Chambord in a small saucepan, and the jam so it can liquefy. When it is cool, I add the puree, so it tastes fresh, not cooked. The Cake Bible recipe calls for up to 1 cup of flavored liqueur, so this works perfectly. Just don't add it hot or you'll melt your butter. 
I've never used any of the buttercream recipes on Cake central, so I can't give you any guidance there. 
The Cake Bible is a book - usually the library has it or any bookstore.
The Italian Buttercream is excellent and I add in a recipe of Raspberry Puree. It is a lot of work and you have to follow the recipes to a "T" and weighing all ingredients insures you always get the same results.
Happy Baking,
Lori V.
Pastries By Vreeke
I have a recipe (somewhere...can't find it) where you take raspberry yogurt and add it to some other ingredients, to make a mousse like filling.
Don't know if this is what you're looking for, but I just made a cake with raspberry jam, cream cheese and Cool Whip. It was delicious. I made it with a lemon cake. Problem is...you have to refrigerate it, so depending on the size of your cake, it could be a problem. Let me know if you want the recipe.
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