pickle jar terrarium - wonder how long they last - seems like it would run out of air or nutrients or something, and once you unscrew the jar again, you wreck it - but maybe as a more ephemeral terrarium project. and it's just a pickle jar!
*Colored ice balls* Fill balloons with water and add food coloring- red and green would be great around christmas! (be careful not to let the food coloring escape!), once frozen cut the balloons off and voila! Look like giant marbles :)