Old worn out sheets...they breath, don't scratch and hide it from casual observation when the door is open.

 

HD touring bike dust cover.Been using it for the last 5 years with no moisture problems.Bike is stored in a non heated garage all winter.

 

I like the paper car covers, the ones with the open mesh that breath real good. Sort of like the white paper ones new bikes get shipped to dealer in. In fact you could go down there and as for one, they just throw them away. What's nice about the car covers is they are plenty big enough to roll the bike on, then tie it up top for a good complete fit. Gives good access too if you need to take a peek, etc. I think last time I got one it was like $25.00 ?