After a recent Lannan Readings & Conversations evening, we were discussing what conditions were well-suited to a creative life. We didn't come to any hard and fast conclusions (other than that television should be kept to a minimum), but there are tools out there to facilitate creativity, especially of a literary stripe.
You can try the Almost Totally Random Writing Exercise Generator which provides style, length and vocabulary prompts that can work as writing inspiration. Cybernetic Engines has prompts that consist of "unusual thoughts". Language is a Virus has a writing prompt generator, and a number of creative writing widgets that you can bookmark or add to a site. Seventh Sanctum has a generator that you can tweak by complexity and number of prompts, and print out the results.
If you need inspiration for a younger crowd, the Imagination Prompt Generator is a good tool, as is this page of prompt generators. In fact, doing a Google search for "writing generator" or "writing prompt" or "creativity generator" will turn up dozens of sites that should spark something in your imagination, regardless of which art you practice. If you're still stuck, DMOZ's directory of writing exercises might be the place to start.
And if all else fails, you can settle for the Amazing Bad Commercial Generator. After all, who says that creativity has to be good?