Here comes a very easy activity for pre-schoolers, and it can be done very easily at home. Simply draw something simple in a piece of paper, and have your child gluing small pieces of paper (preferably colored) into it.
The only thing you have to take into account is the glue. I tried different kinds of glue, and some of them are really too difficult to be used by 2 or 4 year-olds. Either the glue gets dry and stuck very easily, or you have to be Superman to get some glue out of the bottle. Now we are using Pritt in a liquid version, and that works fine even for Anna.