I had just enough time to make a quick Halloween decoration today:
I mixed equal parts portland cement, peat moss, and perlite (yes, not the healthiest/friendliest ingredients) with some water and put it into a form I made for this purpose several years ago:
Then I added in some rebar bits I had and in a few hours we'll carve a few details (maybe some scrollwork? Maybe a silly name like: Brainzar Tastee or whatever). This mixture makes a very lightweight cement.
We have about 5 or 6 of these and they're great because of light they are. The rebar works great for standing them up in the yard.