I've finished coating three of the four sides with cement. One side left plus the top. Not sure yet what I'll be doing with the top. Once the entire structure is coated with cement, I'll be moving on to the tiling.
Still need lots of tiles, so drop by for June's First Friday to decorate one if you haven't already done so. The edges and the receses will be tiled with pennies. The rest of the facades will be tiled. Judging from the tiles I've already received, it will be fantastic!
There have been a few more evolutions. Now I'm considering having the entire structure on a "Lazy Susan" so it can rotate and be visible from all sides without having to sit in the middle of a room. More work, but I think that will add to the interactive nature of the piece and involve the community even further, on the level of viewer as well as collaborator.
Time to start thinking more about the area surrounding the structure where the Penny Pool/Penny Fountain will be. I'm thinking astro-turf. That may evolve too...