I often find myself drawn to square crops, although I've never shot with a native square camera (well, not since kindergarten). The recent thread on the topic inspired me to post a few of my mine. These are from Rio de Janeiro a few years ago. C&C appreciated!
PS A propos of the discussion of square viewfinding, I thought I'd mention that the GH2 actually has a square mode for the EVF. It's just a crop of the 4:3 rectangle (unlike the 4:3, 3:2, and 16:9 modes, each of which actually go to the edge of the image circle), but it could be helpful for composing.