I want to use it as a cake filling for a fondant covered cake (haven't decided on the icing yet, suggestions?)

Will it be alright to leave the cake out for the next day? If not, I need suggestions for a new filling for marble wedding cake that can be left out.

had the same question. I am doing a cake for Sat. that is too big for my fridge - can it sit out with ganache overnight?

I'm not a professional, but I have worked in bakeries my whole life. The ganache that we have made is made from chocolate chips and heavy whipping cream. Being that it has a dairy product in it, I wouldn't want to leave it out overnight. We always refrigetrate the leftover that we don't use and store all cakes in the fridge, too. But our icing has real butter, cream cheese and heavy whipping cream in it and it's left out, so I'm not to sure. It seems that if you have the room fairly cool, it'd be ok. My concern would be more with the ganache "melting" into the soft texture of the cake and then not having a filling.

I have left my ganache out over night and it's fine. The only problem you might find is if it's whipped ganache and there is a large ratio of cream to choc. the whipped cream part might break down. But if it 1:3 ratio or something similar, it should be fine. Also, putting poured ganache in the fridge will cause the cake to lose the shininess when you take it out.