Make a project that:
Find a project that uses broadcasting and remix it. For example, you could remix this pass-it-on project
Create a sprite that reacts whenever the mouse pointer gets too close. If you leave the sprite alone for a few seconds, it should react differently.
includes three separate scenes that a sprite moves through.
uses the string blocks in the Operators category (i.e., join, letter of, and length of) for some fun wordplay.
shows different backgrounds depending on how loud the room is
answers the user's questions
asks the user to type in multiple words or numbers, stores the items in a list, then does something interesting with the items from the list.
Using one or more of the and, or, and not Operators blocks, create a project that when multiple conditions have been satisfied, a secret is revealed.
uses the cloning features of Scratch. For example, you could make a project that represents a natural or human-made phenomenon.
More projects here
Source: Getting Unstuck by Creative Computing Lab at the Harvard Graduate School of Education.