[bibanez]

A mobius strip made out of paper has 2 sides, the usual one and the edge.

[tines]

You can make it out of some other material that you can smooth, i.e. so that it doesn’t have edges.

[tines]

Come to think of it, doesn't a sphere have only one side?

[WJW]

How about things like Klein bottles that have no edges? (Although I guess that unlike a Mobius strip it's not possible to make a real one here on Earth so the quote from OP still holds)