I have had a few inquiries about how to attach things to outside walls, like signs, wires and Christmas lights without causing any damage.
For a brick wall there is a wonderful gadget called the Brick Clip that simply has a spring on the bottom and teeth on the top which grab a brick by inserting the two ends into the mortar joint. This is great for indoor brick walls where you might want to hang pictures without leaving a mark.
You can also find a little nail on a plastic clip that has three little pin nails built into it and it will hold securely into ordinary brick. I got this one from Lee Valley Tools.
For the vinyl and aluminium siding, just run a short screw up through the vent holes and wrap an attachment wire to it. This way, you don't have to make any new holes in the wall and it can be removed without leaving a mark.