Two-sided Objects from Blender to Unity3d

I have an object that is a modelled cylinder with no end caps. The inside of the cylinder is invisible. is there an easy way to fix this?

I would suggest not using Cull Off as your lighting will be messed up, instead double up the geometry of the model, so actually add internal faces on the inside - there will be no z-fighting if they face different directions so don't worry about that, then it will be lit correctly.

Yes. Add "Cull Off" in your SubShader/Pass, if the inside matches the outside. If you don't need to see the outside, just flip the normals.