I am so bad about knowing what does and doesn't need refrigeration. For instance, a can of frosting says "refrigerate after opening", but a cake with that frosting on it can stay out of the fridge?

So now, my question is this. Can I use pudding as a filling in a cake that I am not refrigerating?

Does anyone have any guidelines or helpful hints on what does and doesn't need refrigeration?

I don't know about the frosting questions, put I would definately not put pudding or mousse in a cake (made with milk or heavy cream) that is being left out. I do leave my buttercream cakes out (use real butter), but only if I have used the sleeve fillings. So I know its safe. I usually will also freeze cake if I have to travel any ways so it will stay good until I get it to a destination. I think I read somewhere here that cakes should not be out of frig for more than four hours if requiring refrigeration. Some one can clarify that if I am wrong.

First, you need to know that manufacturers recommend refrigeration for all kinds of products that really don't need it. Since no one can predict how people are going to store the opened container or for how long, the manufacturer makes this recommendation just to be safe.

Some things really will go bad quicker at room temp. Canned frosting will spoil faster if not refrigerated, but it won't happen immediately.

FYI - some of the things that can be left out of the frig for a long time (days) are mustard, ketchup, jams and jellies, real butter, eggs, nuts, salad dressings - pretty much anything you keep in the door.

There are so many exceptions, it's hard to state any blanket rules on refrigeration.

You cannot use pudding in a cake that won't be refrigerated. Not only will the pudding spoil, it will more than likely be 'absorbed' into the cake making a horrible, yet delicious, mess.

Don't be fooled by puddings sold at room temp. They are vacuum sealed to retard spoilage. Once opened, they're as vulnerable as any other milk-based product and need to be refrigerated.

Sleeve fillings don't need refrigeration in the cake, however, leftovers should be stored in the frig.

Generally, anything with whipped cream needs refrigeration. However, ganache, which is nothing more than unwhipped cream and chocolate does NOT need refrigeration.

That was extrememly helpful.. Thank you to you both!