I need to make a three layer cake today for a out of town party on Saturday. What is the best way to keep this cake fresh until I ice it on Saturday?

I would keep it covered in fridge. Or if you have plenty of time on sat to frost. Freeze the cake, take out sat morning or friday evening and decorate it saturday.

If you can't crumb coat it today (icing or crumb coating a cake actually seals the cake and helps keep it 'fresh'), then I agree with keeping it frozen until sat morning, when you plan to ice it. Depending on the sizes, most cakes will thaw within an hour.